Methods and systems for efficient engine torque control

ABSTRACT

Method and systems are provided for adjusting an engine torque in response to changes in a desired engine torque. In one example, a method may comprise responsive to increasing desired engine torques, monotonically decreasing an alternator torque to a first level from a second level when not injecting fuel to engine cylinders, and stepping up the alternator torque from the first level to the second level while initiating engine combustion, and then monotonically decreasing the alternator torque from the second level to the first level in response to the alternator torque reaching the first level. In this way, a method may comprise adjusting a load exerted on an engine by an alternator mechanically coupled to said engine during both cylinder combustion, and during non-fueling conditions.

FIELD

The present application relates to methods and systems for controllingthe torque of an internal combustion engine while optimizing fueleconomy.

BACKGROUND/SUMMARY

Speed and torque control systems for internal combustion engines changethrottle position and fuel injection amount to increase or decreaseengine torque to a desired torque. Thus, during engine operatingconditions where the actual delivered engine torque is greater than adriver requested engine torque, the throttle may be adjusted to decreaseairflow to the engine. Accordingly, the fuel injection may be decreased.Because the throttle is coupled to the air intake valve of multiplecylinders through an intake manifold, there is a delay time before thechange in throttle position results in a change in engine torque. Sinceadjusting the throttle position does not provide an immediate change inengine torque, the ignition timing is retarded to provide a fasterresponse time. In the description herein, ignition timing may also bereferred to as spark timing. Further, retarding ignition timing may alsobe referred to as spark retard. Therefore, the throttle position andignition timing may both be adjusted to match the engine torque to thedesired engine torque. In one example, spark retard may be employed inresponse to decreases in the driver requested engine torque. Thus, inorder to provide a more instantaneous response to decreases in thedesired engine torque, the ignition timing may be retarded.

In another example, spark retard may be employed when the driverrequested engine torque increases from a level where fuel injection isoff to a level where fuel injection is turned on. Under engine operatingconditions where the desired engine torque drops below a threshold, suchas during vehicle deceleration, fuel injection may be shut off and thevehicle wheels provide a force necessary to keep the engine running.This strategy is commonly referred to as deceleration fuel shut-off(DFSO), and provides improved fuel efficiency during low engine torqueconditions. However, when the driver requested engine torque increasesabove the threshold where fuel injection is turned back on, the increasein engine torque resulting from the fuel injection may be greater thanthe driver requested increase in engine torque. As a result, in suchconditions, the engine torque may exceed the desired engine torque. Inorder to reduce the delivered torque to more precisely match the driverrequested torque in such conditions, spark retard may be employed.

The inventors herein have recognized that retarding ignition timingreduces fuel economy. In one example, some of the above issues may beaddressed by a method comprising, as a desired engine torque increases,when not injecting fuel to engine cylinders, monotonically decreasing analternator torque to a first level from a second level; and in responseto the alternator torque reaching the first level, stepping up thealternator torque from the first level to the second level whileinitiating engine combustion, and then monotonically decreasing thealternator torque from the second level to the first level. In this way,less spark retard can be used, while still reducing delayed torqueresponse and increasing energy capture in the vehicle battery.

In another representation, a method may comprise: during DFSO, when athrottle valve is in a first position and fuel is not injected to one ormore engine cylinders, monotonically decreasing alternator torque to afirst torque from a second torque as desired engine torque increases upto a first level, and during cylinder combustion, maintaining positionof the throttle valve in a second position and monotonically decreasingalternator torque from the first torque to the second torque as desiredengine torque increases from the first level to a second level. In someexamples, the method may further comprise adjusting the position of thethrottle valve between the second position and a third position asdesired engine torque increases above the second level.

In another representation, the method may additionally compriseretarding spark timing from a desired spark timing during cylindercombustion, when the alternator torque is at the second level, andengine torque is greater than desired.

In this manner, fuel economy is improved by reducing the usage of sparkretard, and a faster engine torque response time is provided byadjusting alternator torque in response to changes in a desired enginetorque. Thus, the alternator torque may be used to adjust engine torqueduring both cylinder combustion, and when fuel is not being injected tothe engine such as during a DFSO condition.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example vehicle system layout.

FIG. 2 shows an example electrical circuit for the vehicle system shownin FIG. 1.

FIG. 3 shows a flow chart of a method for regulating engine torque.

FIG. 4 shows a graph depicting changes in an alternator torque inresponse to changes in engine operating conditions.

FIG. 5 shows a graph depicting changes in an alternator torque and sparkretard in response to changes in engine operating conditions.

DETAILED DESCRIPTION

The following description relates to systems and methods for adjustingengine torque in response to driver requested changes in engine torque.Engine torque may be adjusted by adjusting a fuel injection amount andcorrespondingly an intake air flow, spark timing, and alternator torque.A vehicle system, as shown in FIG. 1, may be configured with analternator that is mechanically coupled to an engine. In one example, acurrent and/or voltage may be applied to a field coil of the alternatorwhich may generate an alternator output current that may then be used topower various electrical loads (e.g., ancillary electrical devices) andcharge one or more batteries as shown in FIG. 2. However, in someexamples, when alternator output current is insufficient to power thevarious electrical loads, current may be drawn from the one or morebatteries may to meet the electric power demands of the electricalloads.

Additionally, since the alternator is mechanically coupled to theengine, the current applied to the field coil of the alternator may beconfigured to adjust a load applied to the engine. Thus, in someexamples, the alternator torque and spark timing may be adjusted toadjust the engine torque in responses to changes in the driver requestedengine torque. For example, in response to decreases in the driverrequested engine torque, a voltage and/or current to the field coil maybe increased to provide an additional load and braking force to theengine as described in the method of FIG. 3. Additionally oralternatively, the spark timing may be retarded to reduce the enginetorque in response to decreases in the driver requested engine torque.

However, the alternator load on the engine is limited to the capacity ofthe vehicle's electrical system to use and/or store the electric powerproduced by the alternator. Thus, as the current and/or voltage appliedto the field coil is increased, the alternator load increases, but sodoes the electric power produced by the alternator. Thus, the vehiclesystem may include two batteries for providing increased storagecapacity for the current and/or voltage produced by the alternator asshown in FIGS. 1-2. As such, the range of voltages and/or current thatmay be applied to the field coil, and therefore the braking forceexerted on the engine by the alternator may be increased.

Therefore, due to the increased braking force provided by thealternator, the usage of spark retard may be reduced. As shown in FIGS.4-5, the driver requested engine torque may change over a duration ofengine use. In some examples, as shown in FIG. 4, within a first rangeof driver requested engine torques only the alternator torque and notthe spark timing may be adjusted to compensate for changes in the driverrequested engine torque and adjust the engine torque to match the driverrequested torque. In other examples, as shown in FIG. 5, the sparktiming may only be retarded, when the alternator torque is at an upperthreshold, fuel injection is at a lower level, and the engine torque isgreater than the driver requested engine torque. In this way, sparkretard may only be used reduce engine torque when increasing thealternator torque to the upper threshold is insufficient to bring aboutthe driver requested decrease in engine torque. As such, the usage ofspark retard may be reduced, and the fuel efficiency of the vehiclesystem may be improved.

FIG. 1 shows a block diagram layout of a vehicle system 10, including avehicle drive-train 20. The blocks shown in FIG. 1, which representcomponents of vehicle system 10, may be connected to one another bysolid lines. The solid lines represent physical and/or electricalconnections. As such, blocks connected to one another by solid lines inFIG. 1, represent components of vehicle system 10 that are directlyphysically, and/or electrically connected to one another. Further,dashed lines in shown in FIG. 1 represent electrical connections betweencontroller 40 of vehicle system 10 and various components of vehiclesystem 10.

Drive-train 20 may be powered by engine 22. In one example, engine 22may be a gasoline engine. In alternate examples, other engineconfigurations may be employed, for example a diesel engine. Engine 22may be started with an engine starting system 24, including a starter.In one example, the starter may include an electrical motor. The startermay be configured to support engine restart at or below a predeterminednear zero threshold speed, for example at or below 50 rpm, or 100 rpm.Starting system 24 may be powered by first battery 51. In some examples,battery 51 may be a lead acid battery. However, in other examples,battery 51 may be a super capacitor. In still further examples battery51, may be any suitable electrical energy storage device, such as abattery, super capacitor, capacitor, etc. Further, battery 51 iselectrically coupled to the starting system 24 for providing power tothe starting system 24 during an engine start and/or restart. Torque ofengine 22 may be adjusted via torque actuators, such as a fuel injector26, throttle valve 25, camshaft (not shown), etc. Specifically, torqueof engine 22 may be controlled by adjusting an amount of intake airflowing to the engine via a position of a throttle valve (not shown), anamount of fuel injected to the engine by fuel injector 26, and a sparktiming.

The position of the throttle valve 25 may be adjusted between a firstposition and a third position, and/or any position therebetween, toadjust the amount of intake air flowing to the engine. Specifically, thethrottle valve 25, may be an electronic valve in communication withcontroller 40, so that the controller 40 may send signals to theelectronic actuator of throttle valve 25, for adjusting the position ofthe valve 25. When the throttle valve 25 is in the third position, agreater amount of intake air flows to the engine than when the throttlevalve 25 in the first position. The throttle valve 25 may be adjusted tothe first position when fuel is not being injected by the fuel injector26. Further, the throttle valve 25 may be adjusted to a second position,which is between the first positon and the third position so that agreater amount of air flows to the engine 22 than in the first position,but less than in the third position, when the amount of fuel injected bythe fuel injector 26 is at a lower first amount. Thus, the amount ofintake air flowing to the engine 22 through the throttle valve 25, mayincrease with increasing deflection of the throttle valve 25 from thefirst position to the third position. Additionally, the spark timing maybe adjusted to adjust the torque output by the engine 22. Specifically,the torque output by the engine 22 may decrease with increasingretardation in spark timing. Thus, the spark timing may be retarded to apoint later in the compression stroke of one or more cylinders of engine22 (e.g., closer to the top dead center position of the one or morecylinder of engine 22), to reduce the power output by engine 22, andthereby reduce the engine torque.

Torque output by engine 22 may be transmitted to torque converter 28 todrive an automatic transmission 30. In some examples, the torqueconverter may be referred to as a component of the transmission. Theoutput of the torque converter 28 may be controlled by torque converterlock-up clutch 34. When torque converter lock-up clutch 34 is fullydisengaged, torque converter 28 transmits torque to automatictransmission 30 via fluid transfer between the torque converter turbineand torque converter impeller, thereby enabling torque multiplication.In contrast, when torque converter lock-up clutch 34 is fully engaged,the engine output torque is directly transferred via the torqueconverter 28 clutch to an input shaft (not shown) of transmission 30.Alternatively, the torque converter lock-up clutch 34 may be partiallyengaged, thereby enabling the amount of torque relayed to thetransmission to be adjusted.

Torque output from the automatic transmission 30 may in turn be relayedto wheels 36 to propel the vehicle. Specifically, automatic transmission30 may adjust an input driving torque at the input shaft (not shown)responsive to a vehicle traveling condition before transmitting anoutput driving torque to the wheels. For example, transmission torquemay be transferred to vehicle wheels 36 by engaging one or moreclutches, including forward clutch 32. As such, a plurality of suchclutches may be engaged, as needed. Further, wheels 36 may be locked byengaging wheel brakes 38. In one example, wheel brakes 38 may be engagedin response to the driver pressing his foot on a brake pedal (notshown). In the same way, wheels 36 may be unlocked by disengaging wheelbrakes 38 in response to the driver releasing his foot from the brakepedal.

Vehicle system components outside of the drivetrain may include analternator 42, the first battery 51, a second battery 46, and auxiliaryelectrical loads 48. Auxiliary electrical loads 48 may include: lights,radio system, HVAC systems (for heating and/or cooling a vehicle cabin),seat heater, rear window heaters, cooling fans, etc. Alternator 42 maybe configured to convert the mechanical energy generated while runningengine 22 to electrical energy for powering the electrical loads 48 andcharging the first and second batteries 51 and 46, respectively. Asdescribed above, first battery 51 may be a lead acid battery. In someexamples, second battery 46 may be a lithium-ion battery. In otherexamples, second battery 46 may be a lead acid battery. In furtherexamples, second battery 46 may be a super capacitor. In still otherexamples, battery 46 may be an suitable electrical energy storage devicesuch as a battery, capacitor, super capacitor, etc.

An air conditioning (A/C) compressor 144 may also be connected to theengine 22. The air conditioning compressor 144 compresses and transfersrefrigerant gas. The engine 22 provides torque to the air conditioningcompressor 144 for operation. The air conditioning compressor 144 may beselectively coupled and decoupled to the engine 22, so that when coupledto the engine 22, the A/C compressor is on, and when decoupled to theengine 22 the A/C compressor is off. The A/C compressor may be coupledto the engine by one or more of a clutch, electronic switch, etc.

Alternator 42 may include a rotor 43, mechanically coupled to the engine22, and a stator 47 electrically coupled to the second battery 46, firstbattery 51, and electrical loads 48. Thus, when engine 22 is on, therotational energy generated by the engine causes the rotor 43 to spinbecause the rotor 43 is mechanically coupled to the engine 22. In apreferred embodiment, the rotor 43 may include a rotor field coil 45.When the engine 22 is on, and the rotor 43 is spinning relative to thestator 47, current applied to the field coil 45 may induce current toflow in the stator 47. In other embodiments, the field coil 45 may beincluded in stator 47, and not the rotor 43. Thus, the output currentmay be induced in the spinning rotor 43, instead of the stationarystator 47. However, in the preferred embodiment, when a voltage isapplied to the field coil 45, and the engine 22 is running, a currentmay be generated in the stator 47. During engine operation, a portion orall of the current output by the stator 47 may flow to field coil 45. Assuch, the alternator 42 may be self-energizing. Once the engine 22 ison, and the rotor 43 is spinning, current generated by the alternator 42may be used to supply the voltage and/or current necessary to energizethe field coil 45, and in turn continue to produce electrical power fromthe alternator 42.

However, before the rotor 43 begins to spin, such as when the engine 22is turned on at a start and/or restart, current to the field coil 45 maybe supplied by an external source, outside of the alternator 42. In oneexample, when the rotor 43 is not spinning such as during an enginestart and/or restart, current to the field coil 45 may be supplied byfirst battery 51. However, in another example, current to the field coil45 may be supplied by second battery 46 at an engine start and/orrestart condition. In other examples, current to the field coil 45 maybe supplied by both first battery 51 and second battery 46 at an enginestart and/or restart condition. In still further examples, thealternator 42 may include its own DC generator (shown below withreference to FIG. 2) for supplying current to the field coil 45 at anengine start and/or restart condition.

During both an engine start and/or restart, and when the engine isrunning, the voltage and/or current provided to the field coil 45 may becontrolled by a first voltage regulator 44. Thus, any current and/orvoltage being supplied to the field coil 45, is regulated and/oradjusted by the voltage regulator 44. The voltage regulator 44 may be aDC/DC converter (or DC/DC converter based device) for example,configured to output a regulated voltage to the field coil 45. In oneexample the voltage regulator 44 may be included within the alternator42. However as shown in the example of FIG. 1, the voltage regulator 44may be external to the alternator 42. Thus, the voltage and/or currentprovided to the field coil 45, and therefore the current output by thestator 47 may be regulated by the voltage regulator 44. Specifically,voltage regulator 44 may be configured to regulate the voltage and/orcurrent that is supplied to the field coil 45 to a set point, where theset point is adjustable based on electrical signals from the controller40 and engine operating conditions.

Controller 40, may be in electrical communication with one or more ofthe first battery 51, second battery 46, electrical loads 48, andvoltage regulator 44. The dashed lines in FIG. 1, represent electricalconnections between the controller 40 and various components of vehiclesystem 10. Controller 40 may send signals to the voltage regulator 44,to adjust the set point (e.g., current and/or voltage supplied to thefield coil 45) based on the electrical power demands of the vehiclesystem 10, which may include on one or more of the charge states of thebatteries 51 and 46, and operational states of the electrical loads 48.As will be explained in greater detail below with reference to FIG. 2,the voltage regulator 44 and/or the controller 40, may be in electricalcommunication with the first battery 51, and second battery 46, forsensing the respective voltage of the batteries, and adjusting thecurrent and/or voltage supplied to the field coil 45, based on thecharge states of the batteries.

However, in other examples, the controller 40 may additionally oralternatively send signals to the voltage regulator 44, to adjust theset point (e.g., current and/or voltage supplied to the field coil 45)based on engine operating conditions as will be explained in greaterdetail below with reference to FIGS. 3-5. Engine operating conditions,as will be discussed in greater detail below with reference to FIG. 3,may include a desired engine torque as input via an input device 192 bya vehicle operator 190, an estimated torque produced by the engine, aspark timing, throttle valve position, fuel injection amount, etc. Thedesired engine torque may be estimated by the controller 40 based oninput from the vehicle operator 190 via the input device. Thus, thedesired engine torque may be based on the position of the acceleratorpedal and brake pedal of input device 192. As will be described below,the fuel injection amount and throttle valve position may be adjustedbased on changes in the position of one or more of the accelerator pedaland brake pedal.

Thus, the controller 40 may additionally or alternatively adjust thecurrent and/or voltage supplied to the field coil 45 via the voltageregulator 44 in response to changes in the desired engine torque. Forexample, as elaborated in greater detail with reference to FIG. 3, thecurrent and/or voltage applied to the field coil 45, and therefore thealternator torque may be increased in response to decreasing desiredengine torque. Further, the alternator torque may be adjusted based on adifference between the desired engine torque and the estimated actualengine torque. The estimated actual engine torque may be estimated bythe controller 40 based on feedback from a plurality of sensors 65 whichmay include one or more of a torque sensor, manifold air flow (MAF)sensor, throttle position sensor, crankshaft position sensor, vehiclespeed sensor, etc. Thus, the actual engine torque delivered by engine22, may be estimated based on the intake mass air flow as estimatedbased on the outputs from a MAF sensor and throttle position sensor,fuel injection amount, crankshaft position, vehicle speed, etc.

Therefore, the controller 40 may determine a desired current and/orvoltage to be supplied to the field coil 45, while the voltage regulator44 may ensure that the actual voltage and or current supplied to thefield coil 45, matches the desired voltage and/or current determined bythe controller 40. In one example, a voltage command from a controller40 may be compared to a voltage output by the alternator 42. As anexample, if the voltage commanded from the controller 40 is greater thanthe voltage output by the alternator 42, the voltage and/or currentapplied to the field coil 45 may be increased, to increase the currentoutput by the stator 47.

When current is generated in the stator 47, an electromotive force isexerted on the rotor 43 by the stator 47, which opposes the rotationalmotion of the rotor 43. Specifically, the current generated in the fieldcoil 45 of the rotor 43, produces a changing magnetic field, whichinduces a current to flow in the stator 47. The current generated in thestator 47, produces a magnetic field which exerts a force on the rotor43 that opposes the rotation of the rotor 43. Said another way,increasing the current and/or voltage supplied to the field coil 45,results in a braking force, which may reduce the speed of the rotor 43.Thus, increasing the current and/or voltage supplied to the field coil45 may result in a greater force required to rotate the rotor 43 of thealternator 42. As such, when a voltage is applied to the alternatorfield coil 45, a load is applied on the engine 22. In one example,decreasing the voltage and/or current applied to the field coil 45 maydecrease the current output by the alternator 42 and decrease the loadapplied to the engine 22. Thus, the load applied to the engine 22 may beadjusted by increasing or decreasing the voltage and/or current appliedto the field coil 45 of the alternator 42. As will be discussed ingreater detail below with reference to FIGS. 3-5, the torque of theengine 22 may be reduced by increasing the voltage and/or currentsupplied to the field coil 45. Similarly, the torque of the engine 22may be increased by decreasing the voltage and/or current supplied tothe field coil 45.

In this way, the torque output by engine 22 may be adjusted by adjustingthe alternator torque. Specifically, the engine torque may be adjustedby adjusting an amount of current and or/voltage supplied to the fieldcoil 45. As explained above, adjusting the current and/or voltagesupplied to the field coil 45, may be performed by adjusting the setpoint of the voltage regulator 44, which may be controlled by controller40. Thus, controller 40 may adjust the set point of the voltageregulator 44 by sending electrical signals to the voltage regulator 44,and thereby adjust the alternator torque exerted on engine 22, which mayin turn result in changes to the torque produced by engine 22. As willbe explained in greater detail below with reference to FIG. 3, thecontroller 40 may adjust the set point of the voltage regulator based onchanges in the desired engine torque. The desired engine torque may bean engine torque requested by the vehicle operator 190 via the inputdevice 192, which may include an accelerator pedal and a brake pedal.Therefore, in much the same way, an amount of fuel injected to engine 22may be adjusted based on vehicle operator input via input device 192, sotoo may the current and/or voltage supplied to the alternator beadjusted. As such, the alternator torque, (e.g., the torque exerted onthe engine by the alternator), may be adjusted based on a desired enginetorque as determined based on input from a vehicle operator 190.Specifically, the alternator torque (e.g., the current and/or voltagesupplied to the field coil 45) may be increased in response to thevehicle operator 190 demanded engine torque decreasing below an actualtorque generated by the engine 22. Thus, in response to changes in thedemanded engine torque, the alternator torque may be adjusted to matchthe actual delivered engine torque to the demanded engine torque.Adjustments to the alternator torque may result in changes in theelectrical energy output from the alternator 42.

The electrical energy output from alternator 42, may be directed to oneor more of the first battery 51, second battery 46, and the electricalloads 48. Thus, the alternator may be used to recharge batteries 51 and46, and power various ancillary electrical loads 48 of the vehiclesystem 10. The first battery 51 and/or second battery 46 may be chargedby alternator 42 only during certain engine operating conditions such asduring DFSO as described in greater detail below with reference to FIG.2. As such, current produced by the alternator 42 may be divided betweenone or more of: the first battery 51, second battery 46, and theelectrical loads 48, based on their respective voltages. As an example,if the second battery 46 is at a lower charge state (e.g., lowervoltage) than the first battery 51, then a greater portion of theelectrical energy produced by the alternator 42 may flow to the secondbattery 46 than the first battery 51. In other engine operatingconditions, alternator 42, may only recharge second battery 46 and notfirst battery 51. In still further examples, the alternator 42 may onlyrecharge first battery 51, and not second battery 46. In still furtherexamples, current produced by the alternator may only flow to power theelectrical loads 48, and not the first battery 51 or second battery 46.However, in other examples, the current produced by the alternator maybe flowed to power the electrical loads 48, and one or more of the firstbattery 51 and second battery 46.

Additionally, as will be described in greater detail below withreference to FIG. 2, first battery 51 and second battery 46 may beelectrically coupled to the electrical loads 48 to provide power to saidelectrical loads 48. Further as described above, first battery 51, maybe electrically coupled to the starting system 24, for providing powerto start the vehicle system 10. First battery 51 and/or second battery46 may provide electrical energy to the electrical loads 48 when thecurrent and/or voltage produced by the alternator 42 is insufficient tomeet the electrical power demands of the electrical loads 48. Thus,during certain engine operating conditions when the power demands fromthe electrical loads 48 exceed the power output by the alternator 42,such as during engine idle, first battery 51 and/or second battery 46may provide all or a portion of the demanded power to the electricalloads 48. As such, the electrical loads 48 may receive power from one ormore of the alternator 42, first battery 51, and second battery 46. Inone example, as depicted, engine 22 may be configured to be selectively(and automatically) shut down when idle-stop conditions are met andrestarted when restart conditions are met. One or more auxiliary loads48 may be maintained, for example, at 12V, even when the engine is off.The power to maintain the auxiliary loads operational when the engine isshut down may be provided, at least in part, by one or more of secondbattery 46 and first battery 51.

In this way, first battery 51, and second battery 46 are capable ofstoring electrical energy produced by the alternator 42, and returningthat energy to the vehicle system 10, when the electrical power producedby the alternator 42 is insufficient to meet the electrical demands ofthe vehicle system 10. As a result, the operational range of currentand/or voltages of the alternator 42 may be increased, due to theincreased electric storage capacity of the vehicle system 10. Saidanother way, by including both the first battery 51 and the secondbattery 46, the electric energy storage capacity of the vehicle system10 may be increased, so that the current and/or voltage produced by thealternator 42 may fluctuate more without resulting in power lossesand/or surges to the electrical loads 48. At higher electric poweroutputs by the alternator 42, where the power output may exceed thepower demand of the electrical loads 48, the first battery 51 and secondbattery 46 can accept a greater amount of electric power, therebyreducing power surges in the vehicle system. Similarly, at lowerelectric power outputs by the alternator 42, where the power output bythe alternator 42 may be less than the power demand of the electricalloads 48, the first battery 51 and second battery 46 may provide agreater amount of electric power, thereby reducing electric power lossesto components of the vehicle system 10. Thus, greater fluctuations inthe alternator current and/or voltage output may be tolerated by thevehicle system 10 without decreasing the performance of the electricalloads 48 of the vehicle system 10.

Because the alternator 42 may be allowed to produce a greater range ofvoltages and/or currents, the alternator torque, and therefore theamount of force capable of being exerted on the engine 22 by thealternator 42 may be increased. As such, the braking force applied tothe engine 22 by the alternator 42 may be increased. As will beexplained in greater detail below with reference to FIGS. 3-5, thealternator torque may therefore be adjusted to provide improved controlof engine torque, while also increasing the fuel efficiency of vehiclesystem 10.

Vehicle system 10 may be controlled at least partially by controller 40and by input from the vehicle operator 190 via the input device 192. Inthe example shown in FIG. 1, input device 192 includes an acceleratorpedal and a brake pedal. Additionally, a pedal position sensor 194 isincluded in the input device 192 for generating a proportional pedalposition signal PP. The accelerator pedal and brake pedal may beadjusted between respective first and second positions and any positionstherebetween. With increasing deflection from the first position to thesecond position of the accelerator pedal, the controller 40 may commandone or more of the following: an increase in the fuel injection amount,increase in intake mass air flow, and decrease in current and/or voltageapplied to the field coil 45 of alternator 42. As described above, thecontroller 40 may adjust the fuel injection amount via the fuel injector26, and may adjust intake mass air flow by adjusting the position of thethrottle valve 25. Conversely, with increasing deflection from the firstposition to the second position of the brake pedal, the controller 40may command one or more of the following: an increase in the voltageand/or current supplied to the alternator field coil 45, decrease infuel injection amount, and decrease in intake mass air flow.

Controller 40 may be a microcomputer including the following: amicroprocessor unit, input/output ports, an electronic storage mediumfor executable programs and calibration values (e.g., a read only memorychip), random access memory, keep alive memory, and a data bus. Thestorage medium read-only memory may be programmed with computer readabledata representing non-transitory instructions executable by themicroprocessor for performing the routines described herein as well asother variants that are anticipated but not specifically listed.Controller 40 may be configured to receive information from a pluralityof sensors 65 and to send control signals to a plurality of actuators 75(various examples of which are described herein). For example, asexplained above, the controller 40 may send a signal to an actuator ofthe throttle valve 25, to adjust the position of the throttle valve 25in response to information received from an input device 192. Otheractuators such as a variety of additional valves and throttles, may becoupled to various locations in the vehicle system 10. Controller 40 mayreceive input data from the various sensors, process the input data, andtrigger the actuators in response to the processed input data based oninstruction or code programmed therein corresponding to one or moreroutines. Example control routines are described herein with regard toFIG. 3.

In some examples, the alternator load can be varied based on controlparameters that are not strictly dependent on engine speed and/ortorque. For example, alternator field voltage and/or current can beadjusted to compensate for engine friction that is related to enginetemperature. Alternatively, the controller 40 can provide a predictableconsistent amount of mechanical load on the engine by substantiallymaintaining a constant voltage to the alternator field coil circuit.However, it should be noted that field current and load provided by thealternator to the engine are not constant when a constant voltage isapplied to the alternator field. Rather, when a constant voltage isapplied to the alternator field coil the alternator field currentchanges with the angular velocity of the rotor. Thus, the current outputby the stator 47, depends on both the voltage and/or current applied tothe field coil 45 and the speed of the engine 22. The load applied tothe engine 22 by the alternator 42 depends on the voltage and/or currentapplied to the field coil 45.

Controller 40 may also adjust an engine torque output by adjusting acombination of spark timing (also referred to herein as ignitiontiming), fuel pulse width, fuel pulse timing, and/or air charge, bycontrolling throttle opening and/or valve timing, valve lift and boostfor turbo- or super-charged engines. In the case of a diesel engine,controller 40 may control the engine torque output by controlling acombination of fuel pulse width, fuel pulse timing, and air charge. Inall cases, engine control may be performed on a cylinder-by-cylinderbasis to control the engine torque output. Further, controller 40 mayuse engine torque actuators (e.g., throttle valve 25 and fuel injector26) along with making adjustments to current supplied to an alternatorfield coil 45 to control engine speed and/or torque during engineoperation. By controlling engine torque actuators and the load appliedto the engine 22 via the alternator 42 it may be possible to control thetorque of the engine 22 to within a desired range during engineoperation.

In this way, a vehicle system may comprise an alternator mechanicallycoupled to an engine, whereby the alternator is configured to convert aportion of the mechanical energy produced by the engine into electricenergy. Specifically, a voltage and/or current supplied to a field coilin a rotor of the alternator may be adjusted to adjust the electricoutput of the alternator. As the rotor spins due to rotational energyproduced by the engine, the current in the field coil produces analternating magnetic field, which in turn induces a current to begenerated in a stator of the alternator. The current generated in thestator produces a magnetic field which exerts a force on the rotor thatopposes the rotation of the rotor. Therefore, a torque is exerted on theengine by the alternator. As the voltage and/or current supplied to thefield coil increases, the alternator torque increases, and therefore thebraking force applied to the engine by the alternator increases.

The vehicle system may further comprise two batteries for storingelectric energy produced by the alternator, and for providing energy toancillary electric devices of the vehicle system. The dual batterysystem may provide increased electric storage capacity for the vehiclesystem. Because of the increased power output by the dual batterysystem, lower alternator torques may be achieved without sacrificingpower supply to the electrical devices. Further, since the dual batterysystem is capable of storing an increased amount of electric power fromthe alternator, higher alternator torques may be achieved while reducingpower surges that may result in degradation of an electrical system ofthe vehicle. As a result, the current and/or voltage applied to thefield coil, and therefore the alternator torque may be varied to agreater degree without sacrificing the function of electric devices inthe vehicle system.

Since the alternator torque may be adjusted between a wider range oftorques, the braking force exerted on the engine by the alternator maybe increased. Because the maximum braking force provided by thealternator on the engine may be increased, alternator torque may be usedto reduce engine torque at higher engine torques. As a result, othermethods for decreasing engine torque, such as the usage of spark retardmay be reduced, and the fuel efficiency of the vehicle system may beimproved.

Turning to FIG. 2, a block diagram layout of an example electricalsystem of vehicle system 10 from FIG. 1 is shown. Components of thevehicle system 10 shown in FIG. 2 may be the same as the componentsshown in FIG. 1. Thus, the components of the vehicle system 10 describedabove with reference to FIG. 1 may not be described in detail againbelow. All connecting lines shown in FIG. 2 represent electricalconnections. As such, any components of vehicle system 10 shown coupledto one another may be directly electrically connected to one another.

Controller 40 may be configured to receive information from a pluralityof sensors 65 and to send control signals to a plurality of actuators 75(various examples of which are described herein). For example, thecontroller 40 may estimate the engine torque produced by the engine(e.g., engine 22 shown in FIG. 1) from a plurality of sensors such as anMAF sensor, throttle position sensor, crankshaft position sensor, torquesensor, vehicle speed sensor, etc. Based on the information receivedfrom the plurality of sensors 65, and from input via a vehicle operator(e.g., vehicle operator 192 shown in FIG. 1), the controller 40 sendcontrol signals to one or more of a throttle valve (e.g., throttle valve25 shown in FIG. 1), fuel injector (e.g., fuel injector 26 shown in FIG.1), and the voltage regulator 44 for adjusting the torque output by theengine (e.g., engine 22 shown in FIG. 1).

The controller 40 may be in electric communication with the firstbattery 51, second battery 46, electrical loads 48, voltage regulator44, an ignition switch 210, and a control circuit 212. The electricalloads 48 may include ancillary electrical devices such as pumps,heaters, fans, radio, power steering, etc. In some examples, thecontroller may be powered by one or more of the first battery 51 andsecond battery 46. In still further examples, the controller 40 may haveits own power source. The voltage regulator 44 may be electricallycoupled to the field coil 45 of alternator 42, and one or more of thefirst battery 51 and second battery 46 for sensing voltages output bythe first and second batteries, respectively, and relaying the sensedvoltages to the controller 40. However, in other examples the controller40 may be directly coupled to the first battery 51 and second battery46, for sensing the voltages of the respective batteries. Controller 40may send signals to the voltage regulator 44 to adjust the voltageand/or current to the alternator field coil 45 based on the sensedvoltages of the first battery 51 and second battery 46, and on the powerdemands of the electrical loads 48. In still further examples, asexplained above with reference to FIG. 1, the controller 40 may adjustthe voltage and/or current supplied to the alternator field coil 45based on a desired engine torque and an estimated engine torque.

When an engine is not spinning (e.g., engine 22 shown in FIG. 1) currentand/or voltage may be supplied to the field coil 45 by one or more ofthe first battery 51 and second battery 46. Specifically an ignitionswitch 210 may be provided in an electric path between the secondbattery 46 and the voltage regulator 44, and/or between the firstbattery 51. The ignition switch may be adjusted between a first position(shown by the dotted line 211 in FIG. 2), in which electric currentflows from the second battery 46 to the voltage regulator 44, and asecond position (shown by the solid line 213 in FIG. 2), in whichelectric current does not flow from the second battery 46 to the voltageregulator 44. When the engine is not spinning, the controller 40 maysignal to an actuator of the ignition switch 210 to adjust the positionof the ignition switch 210 to the first position 211. However, once theengine is running, the voltage and/or current supplied to the field coilmay be produced by the stator 47. Thus as described above with referenceto FIG. 1, the alternator 42 may be self-energizing once the engine ison and is producing rotational energy. However, in other examples, thealternator 42 may include its own exciter circuit 202 which may supplythe voltage to the field coil 45, when the engine is not spinning. Theexciter circuit 202 may be a DC generator or other DC current powersource.

When a voltage and/or current is applied to the alternator field coil45, an alternating magnetic field may be produced by the field coil 45,which may induce current to flow in the stator 47. The stator 47 maycomprise coil windings, configured to output current to power theelectrical loads 48, and charge one or more of the first battery 51 andsecond battery 46. During engine operation, the voltage and/or currentto the alternator field coil 45 may be modulated by commands from thecontroller 40 to the voltage regulator 44 depending on the currentdemands of the electrical system of vehicle system 10 which may compriseone or more of the first battery 51, second battery 46, and electricalloads 48. As an example, if the controller 40 determines that thecurrent and/or voltage output by the alternator 42 exceeds the currentand/or voltage draw from the first battery 51, second battery 46 andelectrical loads 48, then the controller may signal to the voltageregulator 44 to reduce the voltage and/or current to the field coil 45.In another example, if the controller 40 determines that the currentoutput by the alternator 42 is less than the currents demands of theelectrical loads 48, the controller may signal to the voltage regulatorto increase the voltage and/or current to the field coil 45.

Said another way, the voltage regulator 44, may vary a current appliedto the field coil 45 to produce a constant voltage in the current outputby the alternator 42. In some examples, the first battery 51 and/orsecond battery 46 may also be used to supplement electrical power outputfrom the alternator 42, if the current demand from the electrical loads48 is greater than the current output by the alternator 42. Said anotherway, the first battery 51 and/or second battery 46 may supply additionalelectrical power to the electrical loads 48 if the current demand fromthe electrical loads 48 exceeds the current output by the alternator 42.Thus, in some examples, the controller 40 may sense the voltage (e.g.,charge state) of the first battery 51 and second battery 46, and controlthe current and/or voltage applied to the field coil 45 to achieve aconstant state of charge on the first and second batteries 51 and 46,respectively.

During engine operating conditions when the engine torque decreasesbelow a threshold such as during engine idle, engine stop, and/or DFSO,a voltage sufficient to power all of the electrical loads 48 of thevehicle system 10 may continue to be applied to the field coil 45. Inother examples, at engine idle, a voltage sufficient to power all of theelectrical loads 48 and charge one or more of the first battery 51 andthe second battery 46 of the vehicle system 10 may be applied to thefield coil 45. In still further examples, at engine idle, a voltagesufficient to charge one or more of the first battery 51 and secondbattery 46 but not all of the electrical loads 48 of the vehicle system10 may be applied to the field coil 45. In other examples, the currentapplied to the field coil 45 may drop to approximately zero when enginetorque decreases below the threshold, and one or more of the firstbattery 51 and second battery 46 may be used to supply all of theelectrical power needs of the electrical loads 48.

Thus, controller 40 may receive signals relating to the charge state ofthe first battery 51, second battery 46, power demands from theelectrical loads 48, and current output from the stator 47 of alternator42. Additionally, the controller 40 may estimate and/or measure engineoperating conditions based on feedback from a plurality of sensors 65 asdescribed above. In this way, controller 40 may adjust the voltageand/or current to the alternator field coil 45, and thereby the currentoutput by the alternator 42, based on engine operating conditions, powerdemands from the electrical loads 48 and the charge state of firstbattery 51 and second battery 46.

As described above, current and/or voltage generated by alternator 42,may directed to one or more of first battery 51 and second battery 46based on the voltages of the batteries. However, current flow from thealternator 42 to the first battery 51, may additionally be regulated bythe control circuit 212. Specifically, the control circuit 212 maycomprise a diode 214, and a diode bypass 216. The diode 214 may beconfigured to provide unidirectional current flow in the vehicle system10. The diode 214 is depicted in the example of FIG. 2 as an arrow,where the direction of current flow through the diode 214 is in thedirection that the arrow points. Thus, current may only flow through thediode 214 from the first battery 51 to the electrical loads 48. As such,current may not flow from the alternator 42 to the first battery 51through the diode 214. However, current may flow around the diode 214through the diode bypass 216, when the bypass is adjusted to a firstposition, shown in FIG. 2 as the dotted line 217. The position of bypass216 may be controlled by controller 40. Thus, controller 40 may sendsignals to an actuator of bypass 216 for adjusting the position of thebypass 216. The position of bypass 216 may be adjusted between the firstposition in which current may flow from the alternator 42 to the firstbattery 51, and a second position, in which current may not flow fromthe alternator 42 to the first battery 51. In this way, when bypass 216is adjusted to the first position, current may flow bi-directionallybetween the first battery 51, and one or more of the alternator 42 andthe electrical loads 48. However, when bypass 216 is adjusted to thesecond position, current may only flow from the first battery 51 to oneor more of the alternator 42 and the electrical loads 48, and not fromone or more of the second battery 46 and the alternator 42 to the firstbattery 51.

The controller 40 may send signals to the bypass 216 to adjust theposition of the bypass 216 based on engine operating conditions such asthe engine torque, engine speed, engine operational status, etc. Forexample, if the desired engine speed and/or torque of the enginedecreases based on input from the vehicle operator by more than athreshold, such as during DFSO, fuel injection may be turned off, intakemass air flow may be decreased, and alternator torque may be increased.In response to the, increased alternator torque, and therefore increasedelectric power output by alternator 42, bypass 216 may be adjusted tothe first position so that all or a portion of the electric powergenerated by the alternator 42 may be directed to the first battery 51for charging the battery. In other examples, the controller may adjustthe position of the bypass 216 additionally based on the sensed voltageof the first battery 51. For example, if the vehicle system 10 enters aDFSO condition, the controller may not adjust the bypass 216 to thefirst position, and may not flow electric power from the alternator 42to the first battery 51, if the sensed voltage of the battery 51 isgreater than a threshold. Thus, the controller may adjust the bypass 216based on both engine operating conditions and the charge state of thefirst battery 51. If the battery 51 is sufficiently charged, thecontroller may restrict current flow from the alternator 42 to the firstbattery 51.

In another example, the controller 40 may adjust the position of thebypass 216 to the first position at engine idle, and/or a vehicle stop.Thus, when the engine is in idle, the power generated by the alternator42 may be insufficient to meet the demands of the electrical loads 48.Therefore, the controller 40 may adjust the position of the bypass 216to the first position so that the first battery 51 may provide voltageand/or current to the electrical loads 48.

The controller may adjust the position of the bypass 216 to the secondposition at an engine start and/or restart when the engine is notrunning. As such, since current may not flow from the second battery 46to either the first battery 51 or the starting system 24, and all of theelectric energy output by the second battery 46 may be directed to theelectrical loads 48. Further, first battery 51 may provide power to thestarting system 24.

In this way, the controller may regulate the current and/or voltagesupplied to the field coil 45, based on the electric power demands ofthe vehicle system 10, and on engine operating conditions. Thus, thealternator torque may be adjusted to meet the electric power demands ofthe vehicle system 10, and to control the engine torque to a desiredengine torque as estimated by the controller 40.

FIG. 3 shows a flow chart of a method 300 for adjusting an engine torquein response to changes in engine operating conditions. Instructions forcarrying out method 300 may be stored in a memory of an enginecontroller such as controller 40 shown in FIGS. 1-2. Further, method 300may be executed by the controller. Instructions for carrying out method300 may be executed by a controller based on instructions stored on amemory of the controller and in conjunction with signals received fromsensors of the engine system, such as the sensors described above withreference to FIG. 1. The controller may employ engine actuators of theengine system to adjust engine operation, according to the methodsdescribed below.

Method 300 begins at 302 and the controller (e.g., controller 40)estimates and/or measures engine operating conditions based on feedbackfrom a plurality of sensors (e.g., sensors 65). Engine operatingconditions may include, engine speed, engine load, engine torque, engineload, intake mass air flow, manifold pressure, a position of a throttlevalve, a position of a brake pedal, a position of an accelerator pedal,etc.

After estimating and/or measuring engine operating conditions the method300 proceeds to 304 and includes determining if a desired engine torqueis greater than an upper first threshold. As described above withreference to FIG. 1, the desired engine torque may be an engine torquerequested by a vehicle operator (e.g., vehicle operator 190 shown inFIG. 1) via an input device (e.g., input device 192). For example theinput device may include an accelerator pedal and a brake pedal. Thus,the desired engine torque may be based on the position of theaccelerator pedal and brake pedal of input device. Both the acceleratorpedal and brake pedal may be adjusted between respective first andsecond positions. The desired engine torque may increase with increasingdeflection of the accelerator pedal from the first position to thesecond position and increasing deflection of the brake pedal from thesecond position to the first position. The first position may representa position in which the respective pedal is not depressed by the vehicleoperator, and the second position may represent a position of the pedalwhere the pedal is fully depressed by the vehicle operator. As thevehicle operator depresses the accelerator pedal, the desired enginetorque may increase. Similarly as the vehicle operator depressed thebrake pedal, the desired engine torque may decrease. The positions ofthe brake pedal and accelerator pedal may be measured by a pedalposition sensor (e.g., pedal position sensor 194 shown in FIG. 1), whichmay be relayed to the controller. Thus, based on the positions of thebrake and accelerator pedals of the input device 192, the controller maydetermine the desired engine torque. Specifically, the controller maydetermine the desired engine torque based on a look-up table stored incomputer readable memory relating the position of the input device 192to desired engine torques.

The upper first threshold may represent approximately a zero-thresholdtorque level.

Thus, the upper first threshold may be approximately zero. As such,engine torque above the first threshold may be positive engine torque,where the engine speed may be increasing. On the other hand, enginetorques below the first threshold may be negative engine torques wherethe engine speed may be decreasing.

If it is determined at 304 that the desired engine torque is greaterthan the upper first threshold, then method 300 may proceed to 306 whichcomprises adjusting a fuel injection amount and throttle valve positionbased on the desired engine torque. Specifically, the method at 306comprises adjusting an amount of fuel injected into an engine (e.g.,engine 22 shown in FIG. 1), between a lower first amount and a highersecond amount based on changes in the desired engine torque, where thesecond amount is greater than the first amount. As such the controllermay send signals to one or more fuel injectors (e.g., fuel injector 26shown in FIG. 1), to monotonically increase the amount of fuel injectedto the engine for increases in the desired engine torque. Thus, the fuelinjection amount may be proportionate to the desired engine torque, withfuel injection increasing with increasing desired engine torque, anddecreasing with decreasing desired engine torque. However, in someexamples, the fuel injection amount may not exceed the second amount.Similarly the position of the throttle valve (e.g., throttle valve 25shown in FIG. 1) may be adjusted between a second position and a thirdposition based on changes in the desired engine torque at 306. Theamount of intake air flowing to the engine may increase with increasingdeflection from the second position to the third position. Thus, whenthe throttle valve is in the third position, more air may flow to theengine than when the throttle valve is in the second position.

The controller may send signals to an actuator of the throttle valve toadjust the position of the throttle valve based on the desired enginetorque, and a relationship between fuel injection amount and throttleposition which may be stored in a look-up table stored in the memory ofthe controller. The relationship between the fuel injection amount andthrottle position may be based on a desired air/fuel ratio. Thus, basedon the desired engine torque, the controller may determine a desired airflow and fuel injection amount based on a desired air/fuel ratio. Insome examples the air/fuel ratio may be stoichiometric and may beapproximately 14.7:1. However in other examples the air/fuel ratio maybe greater and/or less than stoichiometric. Therefore, based on thedesired an engine torque, and a desired air/fuel ratio, the controllermay send signals to the throttle valve actuator to adjust the positionof the throttle valve, and to the fuel injector to adjust an amount offuel to be injected to the engine, so that the desired engine torque andair/fuel ratio may be maintained. For increases in engine torque abovethe upper first threshold, the position of the throttle valve may beadjusted with increasing deflection from the second position towards thethird position, and the fuel injection amount may be increased accordingto the desired air/fuel ratio. Similarly, for decreases in engine torqueabove the upper first threshold, the position of the throttle valve maybe adjusted with increasing deflection from the third position towardsthe second position, and the fuel injection amount may be decreasedaccording to the desired air/fuel ratio.

Method 300 may then continue from 306 to 308 which comprises maintainingalternator torque to a lower first level. As discussed above withreference to FIG. 1, a rotor (e.g., rotor 43) of an alternator (e.g.,alternator 42) may be mechanically coupled to the engine. The controllermay adjust the alternator torque by adjusting the voltage supplied to analternator field coil (e.g., alternator field coil 45). In one example,the controller may adjust the set point of a voltage regulator (e.g.,voltage regulator 44) at 411. Adjusting the set point of the voltageregulator may adjust the voltage and/or current supplied to the fieldcoil of the alternator. Since adjusting the current and/or voltagesupplied to the field coil results in adjustments to the load exerted onthe engine by the alternator, adjusting of the current and/or voltagesupplied to the field coil may also be referred to as adjusting thealternator torque. Thus, increasing the alternator torque may be used todescribe increasing the voltage and/or current supplied to the fieldcoil. In this way, the method 300 at 308 may include adjusting thevoltage and/or current supplied to the field coil to a lower firstlevel. The lower first level of the voltage and/or current supplied tothe field coil may be a voltage and/or current sufficient to generate aresulting power output of the alternator that may provide all or aportion of the power needed to run various ancillary electrical devices(e.g., electrical devices 48 shown in FIGS. 1-2). Additionally oralternatively, the lower first level may be a voltage and/or currentsufficient to provide electric power to one or more batteries (e.g.,first battery 51 and second battery 46 shown in FIGS. 1-2).

It is important to note that method 300 may proceed to 308 beforeexecuting 306. In other examples, method 300 may execute 306 and 308simultaneously. After executing both 306 and 308, method 300 thenreturns.

Returning to 304, if it is determined at 304, that the engine torque isnot greater that the upper first threshold (e.g., is less than the firstthreshold), then method 300 continues to 310 which comprises determiningif the desired engine torque is greater than an intermediate secondthreshold. The intermediate second threshold is less than the upperfirst threshold. The second threshold may an engine torque level storedin the memory of the controller. If it is determined at 310 that theengine torque is above the second threshold, then method 300 maycontinue to 312 which comprises adjusting the alternator torque betweenthe lower first level and an upper second level based on changes in thedesired engine torque between the first and second thresholds. The uppersecond level may be an alternator torque level at which, the currentand/or voltage generated by the alternator is sufficient to powervarious electrical devices (e.g., electrical loads 48 shown in FIGS.1-2) and recharge one or more of a first battery (e.g., first battery 51shown in FIGS. 1-2) and a second battery (e.g., second battery 46 shownin FIGS. 1-2). The alternator torque may be adjusted in inverseproportion to changes in the engine torque. Thus, as the desired enginetorque increases between the first and second threshold, the alternatortorque may decrease, and as the engine torque decreases, the alternatortorque may increase. Said another way, the alternator torquemonotonically decrease with increasing engine torque, and vice versa.

In another example, the alternator torque may additionally oralternatively be adjusted based on a difference between the desiredengine torque and an estimated actual engine torque. As explained abovewith reference to FIG. 1, the estimated actual engine torque, may be anestimate of the current torque output by the engine. The engine torquemay be estimated by the controller based on feedback from one or moresensors (e.g., sensor 65 shown in FIG. 1) such as a torque sensor,manifold air flow (MAF) sensor, throttle position sensor, crankshaftposition sensor, vehicle speed sensor, etc. Thus, the actual enginetorque delivered by the engine, may be estimated based on the intakemass air flow as estimated based on the outputs from a MAF sensor andthrottle position sensor, fuel injection amount, crankshaft position,vehicle speed, etc. In other examples, the engine torque may beestimated by a torque sensor positioned on a crankshaft of the engine.Thus, the alternator torque may be adjusted based on a differencebetween the estimated engine torque and the desired engine torque. Ifthe desired engine torque is less than the estimated engine torque, thenthe voltage and/or current applied to the field coil (e.g., alternatortorque) may be increased to provide a braking force to the engine. Thus,increasing the alternator torque may bring about a correspondingdecrease in engine torque, which may reduce the disparity between thedesired and estimated engine torque. However, if the desired enginetorque is greater than the estimated engine torque, then the alternatortorque may be decreased, to bring about a corresponding increase inengine torque, and more closely match the estimated engine torque to thedesired engine torque.

Thus, the method 300 at 312 comprises adjusting the alternator torquebased on changes in the desired engine torque to match the actual enginetorque more closely with the desired engine torque. In this way, thecurrent and/or voltage supplied to the field coil may be adjusted toregulate the engine torque. Specifically, the current and/or voltagesupplied to the field coil may be monotonically increased to cause adecrease in engine torque in response to decreases in the desired enginetorque and/or in conditions where the desired engine torque is less thanthe estimated engine torque. Similarly, the current and/or voltagesupplied to the field coil may be monotonically decreased to cause anincrease in engine torque in response to increases in the desired enginetorque and/or in condition where the desired engine torque is greaterthan the estimated engine torque.

In other embodiments, the method 300 at 312 may additionally compriseadjusting the spark timing of the engine. However, the spark timing isonly retarded when the alternator torque is at the upper second level,and the desired engine torque is less than the estimated deliveredengine torque. Thus, if increasing the alternator torque to the uppersecond level is insufficient to bring about the required drop in enginetorque to match the delivered engine torque to the desired enginetorque, then the method 300 at 312 may additionally include retardingthe spark timing. Said another way, as the desired engine torquedecreases, the alternator torque may be monotonically increased up tothe upper second level. If the delivered engine torque is still greaterthan the desired engine torque with the alternator torque at the uppersecond level, the spark timing may be retarded to further reduce thedesired engine torque. Specifically, the sparking timing may retardedfrom a set point to a point later in the compression stroke in responseto the desired engine torque decreasing and/or the desired engine torquebeing less than the estimated delivered engine torque. Said another way,the spark timing may be adjusted to a point closer to the top deadcenter position of one or more pistons in one or more engine cylindersof the engine. Thus, increasing the amount of spark retard meansadjusting the spark timing to be closer to the point at which the pistonis at the top dead center position in the compression stroke. The amountof time that the spark timing is retarded in the compression stroke maymonotonically increase with decreasing desired engine torque. That is tosay that, if the alternator torque is at the upper second level, thespark timing may be retarded in proportion to the amount of differencebetween the desired engine torque and the estimated engine torque.Therefore, when the desired engine torque is between the second andthird thresholds, and the alternator torque is at the upper secondlevel, the spark timing may be retarded until the estimated enginetorque matches the desired engine torque. Retarding the spark timing mayreduce the delivered engine torque, since retarding the spark timingreduces the power produced during a full cylinder stroke. The amount ofspark retard may be proportionate to the amount of decrease in thedesired engine torque and/or amount of difference between the desiredengine torque and the estimated engine torque. Thus, the spark retardmay be monotonically increased up to an upper first level for decreasesin the desired engine torque. Said another way, the spark timing may beretarded up to a first level, where the amount of spark retard may beproportional to the amount of decrease in the desired engine torque.

In still further embodiments, the method 300 at 312 may additionally oralternatively comprise supplying power to an A/C compressor (e.g.,A/C/compressor 144 shown in FIG. 1), for providing an additional load onthe engine. Thus, the method 300 at 312 may additionally oralternatively include coupling the A/C compressor to the engine so thatthe engine supplies power to the A/C compressor for cooling a coolant ofthe engine. By coupling the A/C compressor to the engine, at 312, acoolant of the engine may be cooled by the A/C compressor, to reduce theamount of time the A/C compressor is on. Thus, by coupling the A/Ccompressor to the engine when the estimated engine torque is greaterthan desired, the use of the A/C compressor at conditions when theestimated engine torque is not greater than desired may be reduced, andtherefore fuel efficiency may be improved.

Method 300 may then proceed from 312 to 314, which comprises adjustingthe fuel injection to the lower first amount, and adjusting the throttlevalve to the second position. If the fuel injection amount is already atthe lower first amount at 314, then the method 300 at 314 may comprisemaintaining the fuel injection amount at the lower first amount.Similarly, if the throttle valve is already in the second position at314, then the method 300 at 314 may comprise maintaining the position ofthe throttle valve in the second position. If the fuel injection is offat 314, and fuel is not being injected to the engine at 314, then themethod 300 at 314 may comprise initiating engine combustion, andincreasing the fuel injection amount to the lower first amount. As such,when the desired engine torque is between the second threshold and thefirst threshold, the fuel injection amount and air flow to the enginemay be held relatively constant. The fuel injection amount may bemaintained approximately constant the lower first amount, and thethrottle valve may be maintained at the second position so that anapproximately constant amount of intake air may flow to the engine. Itis important to note that method 300 may proceed to 314 before executing312. In other examples, method 300 may execute 312 and 314simultaneously. After 312 and 314 are executed, method 300 then returns.

Returning to 310, if it is determined that the desired engine torque isnot greater than the second threshold (e.g., desired torque is less thanthe second threshold), then method 300 proceeds to 316 which comprisesdetermining if the desired engine torque is greater than an intermediatethird threshold. The intermediate third threshold is less than theintermediate second threshold. However, in some embodiments, the thirdthreshold may be approximately the same as the second threshold, andtherefore the difference between the third threshold and secondthreshold may be nearly zero. Thus, the range of desired engine torquelevels between he second and third thresholds is smaller than the rangeof desired engine torque levels between the first and second thresholds.The third threshold may an engine torque level stored in the memory ofthe controller. If the desired engine torque is greater than the thirdthreshold at 316, and thus the desired engine torque is between thethird and second thresholds, then method 300 continues to 318, which inone example may comprise determining if the desired engine torque isincreasing. When the desired engine torque is between the second andthird thresholds, the method 300 comprises either stepping up thealternator torque from the lower first level to the upper second levelor stepping the alternator torque down from the upper second level tothe lower first level. Additionally, when the alternator torque isbetween the second and third threshold, the method 300 may compriseturning on, or turning of fuel injection. The method 300 at 318comprises determining whether or not to increase the alternator torqueto the upper second level, or decrease the alternator torque to thelower first level. Specifically, in some embodiments, the method 300 at318 may comprise determining if the alternator torque is at the lowerfirst level or the upper second level. In other examples, the method at318 may comprise determining if the desired engine torque is increasingor decreasing between the second and third thresholds. However, in stillfurther embodiments, the method at 318 may comprise determining if thedesired torque is less than, or greater than the estimated deliveredtorque.

If the desired torque is increasing, and/or the desired torque isgreater than the estimated delivered torque, and/or the alternatortorque is at lower first level when the desired torque is between thesecond and third thresholds, then fuel injection may be turned on, andthe alternator torque may be increased to the upper second level whichmay result in an increase in the delivered toque, so as to match thedelivered torque to the desired torque. However, if the desired torqueis less than the estimated delivered torque, and/or the desired torqueis decreasing, and/or the alternator torque is at the upper second levelwhen the desired torque is between the second and third thresholds, thenfuel injection may be turned off, and the alternator torque may bereduced to the lower first level, to bring about a correspondingdecrease in the delivered torque, so that the delivered torque may beadjusted to match the desired torque.

Thus, in one example, the method 300 at 318 may comprise determining ifthe desired engine torque is increasing. Method 300 may be runningcontinuously, such that multiple cycles of method 300 may be executedsequentially. As such, the values of the desired engine torque and/orestimated delivered engine torque over a duration may be stored in thememory of the controller. The duration may include an amount of time,duration of engine use, number of engine cycles, etc. Thus, thecontroller may store in its memory, a dataset of desired engine torquesover a duration. Based on the most recent stored values for the desiredengine torque, the method 300 may include determining if the enginetorque is increasing or decreasing. In some examples, it may bedetermined at 318 of method 300 that the desired engine torque isincreasing if the current desired engine torque is greater than the mostrecent stored engine torque value. In other examples, it may bedetermined that the desired engine torque is increasing if the rate ofdesired engine torque increase is greater than a threshold. Thus, themethod 300 at 318 may include determining if the desired engine torqueis increasing or decreasing by comparing the current desired enginetorque to the engine torques most recently recorded and stored in thememory of the controller. In this way, the values of the desired enginetorque for each iteration of method 300 may be stored over multipleiterations of method 300. If it is determined that the engine torque isincreasing at 318, method 300 may continue to 320 which comprisesadjusting the alternator torque to the upper second level. However, ifit is determined that the engine torque is decreasing at 318, method 300may continue to 321 which comprises adjusting the alternator torque tothe lower first level.

In another embodiment the method 300 at 318 may additionally oralternatively include determining if the desired engine torque isgreater than the estimated delivered engine torque in the mannerdescribed above at 312 of method 300. Thus, in some examples, the method300 at 318 may not include determining if the desired engine torque isincreasing or decreasing, but instead may only include determining ifthe desired engine torque is greater or lower than the estimateddelivered engine torque. If the desired engine torque is greater thanthe estimated delivered engine torque at 318, then method 300 maycontinue to 320 which comprises adjusting the alternator torque to theupper second level. However, if the desired engine torque is less thanthe estimated delivered engine torque at 318, then method 300 maycontinue to 321 which comprises adjusting the alternator torque to thelower first level.

In still further embodiments, the method 300 at 318 may additionally oralternatively include determining if the alternator torque is at thefirst level and/or the second level. The alternator torque level may bedetermined based on commands sent from the controller to the voltageregulator. Thus, since the current and/or voltage supplied to the fieldcoil is set based on signals sent from the controller to the voltageregulator, the current and/or voltage supplied to the field coil, andtherefore the alternator torque may be determined based on the mostrecent signals sent from the controller to the voltage regulator. If thealternator torque is at the first level, then the method 300 maycontinue to 320 which comprises adjusting the alternator torque to theupper second level. However, if the alternator torque is at the secondlevel, then method 300 may continue to 321 which comprises adjusting thealternator torque to the lower first level. Thus, method 300 may proceedfrom 318 to 321 which comprises adjusting the alternator torque to thelower first level, if it is determined at 318 that one or more of theengine torque is decreasing, the desired engine torque is less than theestimated delivered engine torque, and the alternator torque is at theupper second level.

However, method 300 may proceed from 318 to 320 if it is determined at318 that one or more of the engine torque is increasing, the desiredengine torque is greater than the estimated delivered engine torque, andthe alternator torque is at the lower first level. Specifically, themethod 300 at 320 may comprise stepping the current and/or voltageapplied to the alternator field coil from the present current/orvoltage, to the current and/or voltage of the upper second level. Thus,in some examples, the method 300 at 320 may comprise stepping up thealternator torque approximately instantaneously to the upper secondlevel. If the alternator torque is already at the upper second level at320, then the method 300 at 320 may comprise maintaining the alternatortorque at the upper second level. The alternator torque may not exceedthe upper second level. Thus, the current and/or voltage supplied to thealternator field coil at 320 may not exceed the upper second level at320. Thus, the upper second level may represent an alternator torquelevel, above which may result in electric power surges produced by thealternator that could cause degradation of the electrical system of thevehicle. From 320, the method 300 may proceed to 314 which comprisesinitiating engine combustion. Said another way, the method 300 mayproceed to 314 which comprises adjusting fuel injection amount andthrottle valve position in the manner previously described at 314 ofmethod 300. Thus, if the alternator torque is increasing between thethird and fourth thresholds, the fuel injection may be turned on.

In some examples, initiating engine combustion (e.g., turning on thefuel injection) as the desired engine torque increases between the thirdand fourth threshold, may result in the delivered engine torqueincreasing by an amount greater than the increase in the desired enginetorque. Thus, after adjusting fuel injection to the lower first amountat 314, the delivered engine torque may be greater than the desiredengine torque. In such examples, the method 300 may additionally includeretarding the spark timing in the manner described above with referenceto 312 of method 300. Thus, the spark retard may be stepped up to anupper first level, and then may be monotonically decreased until thedelivered engine torque matches the desired engine torque. However, itis important to note that in other embodiments, 320 and 314 may beexecuted simultaneously, while in still further embodiments 314 may beexecuted before 320. After determining that one or more of the enginetorque is increasing, the desired engine torque is greater than theestimated delivered engine torque, and the alternator torque is at thelower first level, and executing both 320 and 314, method 300 thenreturns.

Returning to 318, method 300 may proceed from 318 to 321 if it isdetermined at 318 that one or more of the engine torque is decreasing,the desired engine torque is less than the estimated delivered enginetorque, and the alternator torque is at the upper second level.Specifically, the method 300 at 321 may comprise stepping down thecurrent and/or voltage applied to the alternator field coil from thepresent current/or voltage, to the lower first level. Thus, in someexamples, the method 300 at 321 may comprise stepping down thealternator torque approximately instantaneously to the lower firstlevel. If the alternator torque is already at the lower first level at321, then the method 300 at 321 may comprise maintaining the alternatortorque at the lower first level. From 321, the method 300 may proceed to322 which comprises turning off fuel injection and adjusting thethrottle valve to a first position. Turning off the fuel injection maycomprise the controller sending signals to the one or more fuelinjectors so that approximately zero fuel is injected to the engine.Thus, fuel is not injected to the engine at 322. Consequently thethrottle valve is adjusted to a first position which is a position lessproximate to the third position than the second position. As such, lessintake air may flow to the engine when the throttle valve is in thefirst position than the second and/or third positions. In some examplesthe first position of the throttle valve may permit a threshold amountof air to travel to the engine, where the threshold amount of airrepresents a minimum amount of air to be admitted to the engine belowwhich may result in engine degradation. However, it is important to notethat in other embodiments, 321 and 322 may be executed simultaneously,while in still further embodiments 322 may be executed before 321. Afterdetermining that one or more engine torque is decreasing, the desiredengine torque is less than the estimated delivered engine torque, andthe alternator torque is at the upper second level, and both 321 and 322have been executed, method 300 then returns.

Returning to 316, if it is determined that the desired engine torque isnot greater than the intermediate third threshold (e.g., is less thanthe third threshold), method 300 proceeds to 324 which comprisesdetermining if the desired engine torque is greater than a lower fourththreshold. The lower fourth threshold is less than the intermediatethird threshold. If the desired engine torque is greater than the fourththreshold and is therefore between the fourth and third thresholds, thenmethod 300 may continue to 328 which comprises adjusting the alternatortorque between the first and second levels in proportion to changes inthe desired engine torque in the manner described above at 312 of method300. However, unlike at 312, where in some embodiments, the spark timingmay be retarded, the spark timing is not retarded at 328. Thus themethod 300 at 328 comprises only adjusting alternator torque and notadjusting the spark timing. Method 300 may then proceed from 328 to 322and turn the fuel injection off and adjust the throttle valve to thefirst position at described above at 322 of method 300. However, it isimportant to note that in other embodiments, 328 and 322 may be executedsimultaneously, while in still further embodiments 322 may be executedbefore 328. After determining that the engine torque is between thefourth and third thresholds, and that both 328 and 322 have beenexecuted, method 300 then returns.

Returning to 324, if it is determined that the desired engine torque isnot greater than the fourth threshold (e.g., less than the fourththreshold), then method 300 may proceed to 326 which comprises adjustingalternator torque to the upper second level in the manner describedabove at 320 of method 300. If the alternator torque is already at theupper second level at 326, then the method 300 may comprise maintainingthe alternator torque at the upper second level at 326. Method 300 maythen proceed from 326 to 322 which comprises adjusting the fuelinjection and throttle valve position in the manner described above at322 of method 300. However, it is important to note that in otherembodiments, 326 and 322 may be executed simultaneously, while in stillfurther embodiments 322 may be executed before 326. After determiningthat the engine torque is below the fourth threshold, and that both 326and 322 have been executed, method 300 then returns.

It is important to note that in other embodiment, the blocks 304, 310,316, and 324, may be executed in an order different than that describedabove. Namely, method 300 may continue first to 324 after estimatingand/or measuring engine operating conditions at 302. If the desiredengine torque is determined to be less than the fourth threshold at 324,then method 300 continues to 326 which comprises adjusting thealternator torque to the upper second level, and maintaining fuelinjection off at 322. However, if the desired engine torque isdetermined to be greater than the lower fourth threshold at 324, thenmethod 300 may proceed to 316 and determine if the desired engine torqueis greater than the intermediate third threshold. If the desired enginetorque is determined to be less than the intermediate third threshold,and therefore inbetween the third and fourth thresholds, then method 300continues to 328 as described above and adjusts alternator torquebetween the first and second levels in proportion to changes in desiredengine torque between the fourth and third thresholds. Further, fuelinjection may remain off as described at 322 above. If the desiredengine torque is determined to be greater than the third threshold at316, then may 300 may continue to 310 and determine if the engine torqueis greater than the second threshold. If it is determined at 310 thatthe desired engine torque is less than the second threshold, andtherefore in-between the second and third threshold, then the method 300may continue to 318 as described above. However, if it is determinedthat the desired engine torque is greater than the second threshold at310, method 300 may then continue to 304 and determine if the enginetorque is greater than the upper first threshold. If it is determined at304 that the desired engine torque is not greater than the upper firstthreshold, and is therefore in-between the first and second thresholds,then method 300 continues to 312 as described above. However, if it isdetermined at 304 that the desired engine torque is greater than theupper first threshold then method 300 continues to 306 as describedabove.

In this way, fuel injection may only be turned on if the desired torqueincreases above the second threshold and the delivered engine torque isless than the desired engine torque, and/or if the desired engine torqueis in-between the second and third thresholds and one or more of thedesired engine torque is increasing, the desired engine torque isgreater than the delivered engine torque and the alternator torque is atthe lower first level.

In this way, a method may comprise monotonically decreasing analternator torque from an upper second level to a lower first level, inresponse to increases in a desired engine torque up to a firstthreshold. Upon reaching the lower first level, the alternator torquemay then be stepped up to the upper second level. Fuel injection, andtherefore engine cylinder combustion may also be initiated when steppingup the alternator torque from the lower first level to the upper secondlevel. The method may further comprise adjusting alternator torque ininverse proportion to changes in the desired engine torque above thethreshold. Specifically, the method may comprise monotonicallydecreasing the alternator torque for increases in the desired enginetorque above the threshold. Further, in some example, the method mayadditionally comprise maintaining the alternator torque at the uppersecond level, and retarding spark timing in response an estimateddelivered engine torque being greater than the desired engine torquewhen the desired engine torque is greater than the threshold.

Thus, method 300 comprises adjusting the engine torque delivered by thevehicle engine in response to changes in the desired engine torque asrequested by a vehicle operator. A vehicle operator may request a changein engine torque via an input device which may comprise an acceleratorpedal and a brake pedal. In response to changes in the desired enginetorque, the engine torque may be adjusted to match the desired enginetorque. The engine torque may be adjusted by adjusting one or more of: afuel injection amount and therefore an intake mass air flow, analternator torque, and in some examples a spark timing. Morespecifically, depending on the desired engine torque either the fuelinjection amount, or the alternator torque, may be adjusted. Forexample, for desired engine torques above the first threshold, thealternator torque may be maintained at the lower first level, while thefuel injection amount and therefore the intake mass air flow may beadjusted to compensate for changes in the desired engine torque. Thus,the position of the throttle valve and the amount of fuel injected tothe engine may be adjusted to match the actual delivered engine torqueto a desired engine torque when the desired engine torque is above thefirst threshold. Said another way, as the engine torque fluctuates abovethe first threshold, only the fuel injection amount and intake mass airflow may be adjusted to deliver the desired engine torque.

However, if the engine torque drops below the first threshold, the fuelinjection amount is reduced to the lower first amount. Specifically,when the desired engine torque is below the first threshold, but abovethe second threshold, where the second threshold is less than the firstthreshold, the fuel injection amount and therefore the intake mass airflow is maintained at a constant amount. The fuel injection amount maybe less than the amount of fuel injected at engine torques above thefirst threshold. If the engine torque is decreasing between the firstand second thresholds, then the alternator torque may be increased tomatch the delivered engine torque to the desired engine torque. Saidanother way, as the engine torque fluctuates above the second thresholdand below the first threshold, only the alternator may be adjusted todeliver the desired engine torque. The alternator torque may bemonotonically increased between the first and second levels withdecreasing desired engine torque. Thus, in order to compensate forchanges in the desired engine torque between the first and secondthresholds, only the alternator torque may be adjusted to compensate forchanges in the desired engine torque.

In some examples, if the alternator torque is adjusted to the uppersecond level, but the desired engine torque is between the first andsecond threshold and is less than the estimated delivered engine torque,then the spark timing may be retarded to provide an additional brakingforce to the engine. Spark timing may therefore only be retarded if thedesired engine torque is between the first and second thresholds, andthe alternator torque is not sufficient to bring about a change in thedelivered engine torque such that the delivered engine torque matchesthe desired engine torque.

If the desired engine torque is below the second threshold but above athird threshold, where the third threshold is less than the secondthreshold, the alternator torque be stepped up to upper second level ifthe desired engine torque is increasing, and may be stepped down to thelower first level if the desired engine torque is decreasing. Further,the fuel injection may be turned off if the desired engine torque isdecreasing, and may be turned on if the engine torque is increasing.

If the desired engine torque is below the third threshold, but above thefourth threshold, the alternator torque is adjusted to match thedelivered engine torque to the desired engine torque. Thus, thealternator torque may be adjusted in the same way as when the enginetorque fluctuates above the second threshold and below the firstthreshold. The fuel injection may remain off, and the intake mass airflow may remain constant (e.g., throttle valve position is heldconstant) while the alternator torque may be adjusted to compensate forchanges in the desired engine torque.

If the desired engine torque is below the fourth threshold, thealternator torque may be maintained at the upper second level, and fuelinjection may remain off.

In this way, the alternator torque may be adjusted to regulate thedelivered engine torque both during engine operating conditions wherethe fuel is shut off, and when it is turned on. As such, the usage ofspark retard may be reduced, and in some examples, spark retard may notbe used at all. As described above with reference to FIGS. 1-2, becauseof the increased charge capacity of the vehicle system, the alternatortorque be adjusted between a wider range of values. As such, thealternator may exert a greater braking force of the engine. Due theincreased braking capacitance of the alternator, the alternator torquemay be used to regulate engine torque at increased engine torque levels.Thus, the fuel efficiency of the engine may be improved, due to thereduction in the usage of spark retard.

In this way, a method may comprise, as a desired engine torqueincreases: when not injecting fuel to engine cylinders, monotonicallydecreasing an alternator torque to a first level from a second level;and in response to the alternator torque reaching the first level,stepping up the alternator torque from the first level to the secondlevel while initiating engine combustion, and then monotonicallydecreasing the alternator torque from the second level to the firstlevel. The second level may be higher than the first level. Further, acurrent and/or voltage produced by an alternator at the second level issufficient to power various ancillary electric devices, and charge oneor more batteries. Stepping up the alternator torque from the firstlevel to the second level may be approximately instantaneous.Additionally or alternatively, stepping up the alternator torque fromthe first level to the second level, and the initiating enginecombustion may occur simultaneously. The alternator torque may beadjusted by adjusting a current and/or voltage applied to a field coilof the alternator. Thus, decreasing the alternator torque may comprisedecreasing electrical power applied to a rotor field coil of thealternator. In some example, the method may further after initiatingengine combustion, only monotonically decreasing the alternator torqueand not retarding spark timing.

In another example, initiating engine combustion may comprise adjustinga throttle valve from a first position to a second position, where inthe second position a greater amount of air may flow to the one or moreengine cylinders than in the first position, and increasing an amount offuel injection to a non-zero threshold. Further, in other examples,monotonically decreasing the alternator torque to the first level may bein response to the desired engine torque increasing above a firstthreshold, where below the first threshold, the alternator torque may bemaintained at the second level. In still further examples, the methodmay further comprise during engine combustion, in response to thealternator torque reaching the first level, maintaining the alternatortorque at the first level, and monotonically increasing a fuel injectionamount and intake mass air flow to maintain a desired air/fuel ratio. Insome examples, the desired air/fuel ratio may be approximately 14.7:1.

In another representation a method for adjusting an engine torque tomatch a desired engine torque may comprise: during DFSO, when a throttlevalve is in a first position and fuel is not injected to one or moreengine cylinders, monotonically decreasing alternator torque to a firsttorque from a second torque as desired engine torque increases up to afirst level; and during cylinder combustion, maintaining the position ofthe throttle valve in a second position and monotonically decreasingalternator torque from the first torque to the second torque as desiredengine torque increases from the first level to a second level, andadjusting the position of the throttle valve between the second positionand a third position as desired engine torque increases above the secondlevel. In some examples, the desired engine torque may be an enginetorque requested by a vehicle driver via an input device.

The method may further comprise when maintaining the position of thethrottle valve in the second position, injecting a first amount of fuelto one or more engine cylinders according to a desired air/fuel ratio.In some examples, an intake mass air flow increases with increasingdeflection of the throttle valve from the first position to the secondposition, and from the second position to the third position. Inresponse to the desired torque reaching the second level, the method mayfurther comprise stepping the alternator torque up from the first levelto the second level if the desired torque is decreasing, and steppingdown the alternator torque from the second level to the first level ifthe desired torque is increasing. In still further examples, the methodmay comprise when the desired engine torque is less than the secondlevel, decreasing the alternator torque when engine torque is less thandesired, and increasing alternator torque when engine torque is greaterthan desired. Additionally or alternatively, the method may compriseretarding spark timing from a desired spark timing during cylindercombustion, when the alternator torque is at the second level, andengine torque is greater than desired.

Turning now to FIG. 4, a graph 400 is shown, depicting adjustments to analternator torque based on engine operating conditions. Specifically,graph 400 shows changes in a desired torque at plot 402. The desiredtorque may be an amount of engine torque commanded by a vehicle driver.For example, the desired torque may be estimated by a vehicle controller(e.g., controller 12 from FIG. 1), based on inputs from a vehicle drivervia an input device (e.g., input device 192 shown in FIG. 1) which maycomprise one or more of a brake pedal and an accelerator pedal. Thus, asexplained in greater detail above with reference to FIGS. 1-2, thecontroller may determine a desired torque based on the position of theinput device. In response to changes in the desired torque as requestedby a vehicle driver, an amount of fuel to be injected and an amount ofair to be flowed to the engine may be adjusted to match the driverdemanded torque. Specifically, the controller may determine the desiredfuel injection amounts and air flow rates to match the driver desiredtorque. Changes in the fuel injection amount are shown at plot 402, andchanges in the intake air flow rate are shown at plot 404. Theoperational status of fuel injection and intake mass air flow may beregulated by the controller. The fuel injection amount may be an amountof fuel injected by a fuel injector to one or more engine cylinders ascommanded by the controller. Thus, the controller may determine the fuelinjection amount based on commands sent to one or more fuel injectors.Similarly, the intake mass air flow rates may be estimated based on amass airflow sensor in an intake passage of the engine. In otherexamples, the intake mass air flow rate may be estimated based on aposition of a throttle valve in the intake and a one or more pressuresensors in the intake. The intake air flow rate may be a total mass airflow rate of air and/or an air/fuel mixture entering one or more of anintake manifold and an engine cylinder. Further, the fuel injectionamount may be determined by the controller based on the estimated intakemass air flow rate, and a desired air/fuel ratio. In one example, thedesired air/fuel ratio may be a stoichiometric mixture.

However, in certain engine operating conditions, adjusting the fuelinjection amount, and intake mass air flow rate alone may not besufficient to match the actual delivered engine torque to a driverdemanded torque. Additionally, the desired engine torque may decreasebelow a threshold, where the fuel injection is off and the intakeairflow is reduced to a lower first level. Said another way, the desiredengine torque may be less than the actual engine torque delivered evenwhen no fuel is being injected to the engine. Thus, the actual torquedelivered by the engine may differ from the desired requested by thevehicle driver. Plot 408 shows the torque error, which is the differencebetween the desired engine torque and the actual delivered enginetorque. Level T₀ represents approximately zero torque difference. Assuch, T₀, represents a level where the actual delivered engine torque isapproximately the same as the desired engine torque. Torque error mayfluctuate to below T₀, where the actual delivered engine torque is lessthan the desired engine torque, and to above T₀, where the actualdelivered engine torque is greater than the desired engine torque.

To compensate for changes in the desired engine torque which may resultin the torque error increasing above or decreasing below T₀, thealternator torque may be adjusted. Further, as shown below withreference to FIG. 5, the spark timing may be retarded if adjusting thealternator torque is not sufficient to match the actual delivered enginetorque to the desired engine torque. Said another way, in some examples,the alternator torque, and/or spark timing may be adjusted in additionto, or in place of, adjusting fuel injection, to adjust the torqueoutput by the engine. Plot 410 shows changes in the alternator torque.As explained above with reference to FIGS. 1-3, adjusting the alternatortorque may comprise adjusting the current and/or voltage supplied to analternator field coil (e.g., field coil 45 shown in FIGS. 1-2).Adjusting the current and/or voltage supplied to the alternator fieldcoil, may change the strength of the magnetic field produced by thefield coil, which may in turn may change the load exerted on the engineby the alternator. Specifically, increasing the current and/or voltageapplied to the field coil may increase the alternator torque and therebythe load exerted on the engine by the alternator. Thus, increasing thealternator torque may reduce the engine torque. Conversely, reducing thealternator torque may reduce the load exerted on the engine by thealternator, thereby providing an increase the engine torque. The currentand/or voltage applied to the field coil may be adjusted by a voltageregulator (e.g., voltage regulator 44 shown in FIGS. 1-2) based onsignals received from the controller. Based on torque error, asestimated by the controller, the controller may subsequently sendsignals to the voltage regulator to adjust the current and/or voltageapplied to the field coil, which may comprise adjusting a set point ofthe voltage regulator.

In some examples, as shown below with reference to FIG. 5, the sparkretard may be adjusted by the controller. However, in the example shownin FIG. 4 as seen at plot 412, the spark retard may not be adjusted.Thus, as shown in FIG. 4, only the alternator torque may be adjusted tocompensate for changes in the torque error, and not the spark timing.The spark timing may be adjusted to a set point during normal engineoperating conditions (e.g. when fuel injection is on). The set point isa point during the compression stroke before top dead center. However,the spark timing may be retarded from the set point to a later point inthe compression stroke closer to the top dead center position. Thus, asthe amount of spark retard increases, the spark timing moves closer tothe top dead center position of one or more pistons in the engine. As aresult, the power produced by the engine may be reduced with increasingspark retard. The controller may set the spark timing of the enginebased on the estimate torque error. Further, the controller, may sendsignals to one or more spark plugs in the engine to adjust the timing ofspark.

Turning now to graph 400 before to, the desired engine torque (shown atplot 402) remains below a lower first level D₀. However, the desiredengine torque may increase up to the first level D₀ at t₀. Thus, thedesired engine torque may be increasing before t₀. The lower first levelD₀, may be a threshold level, above which fuel may be injected to theengine to meet the desired torque. As such, fuel injection may remainoff before t₀, as shown at plot 404. Thus, the engine may be in a DFSOcondition before t₀. The intake air flow rate as shown at plot 406, mayremain at approximately a lower first level I₁ before t₀. I₁, may be anair flow rate stored in the memory of the controller to be maintainedwhen fuel injection is off. The alternator torque may be at an uppersecond level A₂, before t₀. The torque error may decrease from an uppersecond level T₂, before t₀, as the desired engine torque increasesbefore t₀. Despite the fuel injection being off before t₀, and thealternator torque remaining at the upper second level A₂, the deliveredengine torque may still exceed the desired engine torque before t₀.However, as the desired engine torque increases before t₀, the torqueerror may decrease from T₂, before t₀. Thus, in response to the torqueerror being greater than T₀ before t₀, the alternator torque may bemaintained at the upper second level, A₂. Spark retard remains at alower first level S₀, before t₀. The lower first level S₀, may be alevel where the spark timing is not retarded at all. Thus, the sparktiming may not be retarded from the set point before t₀.

At t₀, the desired engine torque increases above D₀, and the torqueerror decreases to approximately T₀. In response to the increase indesired engine torque, and the torque error decreasing to approximatelyT₀, the alternator torque may begin to be reduced from the upper secondlevel A₂, at t₀. Fuel injection remains off at t₀, and the intake airflow remains at the lower first level I₁. Further, spark retard remainsat S₀.

Between t₀ and t₁, the desired engine torque increases from D₀, to anintermediate second level D₁. D₁ may represent a torque level abovewhich fuel injection is turned on, and below which fuel injection isturned off. Further, D₁ may represent a torque level, where thealternator torque is either stepped up from A₁ to A₂ if one or more ofthe desired torque is increasing and desired torque is greater than theestimated delivered engine torque, or stepped down from A₁ to A₂ if oneor more of the desired torque is decreasing and desired torque is lessthan the estimated delivered engine torque. As such, desired torquelevel D₁, may represent a torque level in-between the second and thirdthresholds described above with reference to method 300 of FIG. 3. Inresponse to the increase in desired engine torque between t₀ and t₁, thealternator torque is monotonically decreased from the upper second levelA₂, to a lower first level A₁. The lower first level A₁, may be analternator torque level, below which would be insufficient to provideelectrical power to various electrical devices (e.g., electrical loads48 shown in FIGS. 1-2). However in other examples, the lower first levelA₁, may be approximately zero, and the power to support the electricaldevices may come from one or more batteries (e.g., first battery 51 andsecond battery 46 shown in FIGS. 1-2). In still further examples, A₁ maybe a non-zero alternator torque level that may represent a power outputby the alternator that may greater than zero, but may be insufficient topower the electrical devices. As such, a portion of the power to theelectrical devices may be provided by one or more of the batteries.Thus, the alternator torque may be adjusted in inverse proportion to thechange in desired engine torque. Fuel injection remains off at betweent₀ and t₁, and the intake air flow remains at the lower first level I₁.Further, spark retard remains at S₀.

At t₁, the desired engine torque increases above D₁. In response to thedesired engine torque increasing above D₁, engine combustion isinitiated. Thus, in response to the desired engine torque increasingabove D₁, fuel injection is turned on, and the amount of fuel injectedto the engine is increased to a lower level F₀. The lower level F₀ maybe a non-zero amount of fuel injection. The intake air flow may increaseaccording to the increase in fuel injection to maintain a desiredair/fuel ratio. In other examples, the intake air flow may not beincreased, and the lower level F₀, may be an amount of fuel injectionsufficient to maintain a desired air/fuel ratio while not increasing theintake air flow. Thus, the position of the throttle valve may remain inthe same position at t₁, and the fuel injection may be increased to F₀to establish the desired air/fuel ratio. In some examples the desiredair/fuel ratio may be approximately 14.7:1. However in other example thedesired air fuel ratio may be greater or less than 14.7:1. Thus, in theexample shown in FIG. 4, the intake air flow may increased from I₁, to asecond level I₂. Additionally at t₁, the alternator torque may beincreased from A₁, to A₂. In one example, the alternator torque may bestepped up from A₁ to A₂. Said another way, the alternator torque may beincreased from A₁ to A₂, instantaneously, or nearly instantaneously. Insome examples, the alternator torque may be increase from A₁ to A₂ atthe same time as the fuel injection is turned on. Said another way, theincrease of the fuel injection to F₀, and the increase in the alternatortorque to A₂ may be simultaneous. However, in other examples, thealternator torque may be increased from A₁ to A₂ before fuel injectionis turned on. At t₁, the torque error may remain approximately constantat T₀, since fuel injection is turned on, but the alternator torque isincreased.

Said another way, the effect of the increase in fuel injection at t₁ onthe delivered engine torque, may be offset by the increase in alternatortorque. Although the increase in fuel injection and intake air flow att₁ may cause an increase in the delivered torque at t₁, the increase inalternator torque may cause a decrease in delivered torque. Thus, byincreasing the fuel injection, while simultaneously increasing thealternator torque at t₁, the delivered torque may be adjusted to matchthe desired torque. Said another way, increasing the fuel injection att₁, without increasing the alternator torque may result in an increasein delivered torque that would be greater than the increase in thedesired engine torque. As a result, the torque error may be greater thanT₀, if the alternator torque is not increased at t₁. So, at t₁, thedelivered engine torque is approximately the same as the desired enginetorque, and therefore the torque error may remain T₀ (e.g., zero).Further, spark retard remains at S₀.

Between t₁ and t₂, the desired engine torque increases from D₁, tohigher third level D₂. In response to the increase in desired enginetorque between t₁ and t₂, the alternator torque is monotonicallydecreased from the upper second level A₂, to a lower first level A₁ inthe manner similar to between time t₀ and t₁. Thus, the alternatortorque may be adjusted in inverse proportion to the change in desiredengine torque. Fuel injection remains approximately constant at F₀, andthe intake air flow remains approximately constant at I₂. Further, sparkretard remains at S₀. Thus, between t₁ and t₂, although the fuelinjection is on, it may remain at F₀, and instead of increasing the fuelinjection amount and intake air flow to compensate for the increase indesired engine torque, the alternator torque may be reduced. By reducingthe alternator torque between t₁ and t₂, the delivered engine torque maybe increased so that the delivered engine torque is approximately thesame as the desired engine torque. As such, the torque error remainsconstant at T₀, between t₁ and t₂. In this way, the delivered enginetorque may be adjusted to match the desired engine torque withoutadjusting the fuel injection and intake air flow amount. Said anotherway, adjustments to the delivered engine torque may be made by adjustingthe alternator torque only, and not adjusting the spark timing, fuelinjection amount, and intake mass air flow. Therefore, the fuelefficiency may be increased between t₁ and t₂.

At t₂, the desired engine torque increases above D₂. In response to thedesired engine torque increasing above D₂, fuel injection is increasedfrom F₀, to levels above F₀ based on an amount of increase in thedesired engine torque. Accordingly, the intake air flow is increasedfrom I₂ to maintain a desired air/fuel ratio. Additionally at t₂, thealternator torque may be remain at the lower first level A₁. Thus, thealternator torque may remain at a level so that current and/or voltagegenerated by the alternator may be sufficient to power one or more ofthe electrical devices and/or charge the one or more batteries. Asdescribed above, since the throttle valve may be located a distance fromthe engine cylinders, the increase in delivered engine torque due to theincrease in fuel injection and intake air flow at t₂ may not beimmediate. Thus, as shown in the example of FIG. 4 at plot 408, thetorque error may decrease below T₀ to T₁ at t₂. Specifically, thedelivered engine torque may be less than the desired engine torque.However, in other examples, the torque error may remain constant at T₀.Thus, depending on the speed of the intake air flow, and the distancefrom the throttle to the engine cylinders, the delay in the response ofthe delivered engine torque to the increase in fuel injection at t₂ maybe approximately zero, and the increase in fuel injection may provide anearly instantaneous increase in the delivered engine torque. Further,spark retard remains at S₀.

Between t₂ and t₃, the desired engine torque fluctuates above the higherthird level D₂. In response to changes in the desired engine torquebetween t₂ and t₃, the fuel injection amount and intake air flow areadjusted to match the delivered engine torque to the desired enginetorque. Thus, for increases in the desired engine torque, the fuelinjection amount and intake air flow may be monotonically increased.Further, the fuel injection amount and intake air flow may be adjustedto maintain the desired air/fuel ratio. For decreases in the desiredengine torque the fuel injection amount and intake air flow may bemonotonically decreased. Therefore, the fuel injection amount and intakeair flow may be adjusted in proportion to the amount of increase and/ordecrease in the desired engine torque. Further, if at any time betweent₂ and t₃ the desired engine torque diverges from the delivered enginetorque resulting in a torque error greater or less than T₀, the fuelinjection amount and intake air flow may further be adjusted to matchthe delivered engine torque to the desired engine torque. In this way,the fuel injection amount and intake air flow, may constantly beadjusted based on changes in the desired engine torque so that thedelivered engine torque matches the desired engine torque. As anexample, immediately after t₂, the fuel injection amount and intake airflow may be increased until the torque error returns to approximatelyT₀. Thus, immediately after t₂, the torque error may return toapproximately T₀, and may remain relatively the same at T₀, up to t₃.Additionally between t₂ and t₃, the alternator torque may be remain atthe lower first level A₁. Thus, the alternator torque may remain at alevel sufficient to power one or more of the electrical devices and/orcharge the one or more batteries. Further, spark retard remains at S₀.

At t₃, the desired engine torque decreases below D₂. In response to thedesired engine torque decreasing below D₂, fuel injection is reduced toF₀. Accordingly, the intake air flow is reduced to I₂ to maintain adesired air/fuel ratio. Additionally at t₃, the alternator torque maybegin to be increased from the lower first level A₁. Torque error mayremain relatively the same at T₀. Further, spark retard remains at S₀.

Between t₃ and t₄, the desired engine torque decreases from D₂, to D₁.In response to the decrease in desired engine torque between t₃ and t₄,the alternator torque is monotonically increased from the lower firstlevel A₁ to the upper second level A₂. Thus, the alternator torque maybe adjusted in inverse proportion to the change in desired engine torquein much the same way as between t₁ and t₂. However, instead of thedesired torque increasing and the resulting alternator torque decreasingas between t₁ and t₂, the desired torque is decreasing and the resultingalternator torque is increasing between t₃ and t₄. Fuel injectionremains approximately constant at F₀, and the intake air flow remainsapproximately constant at I₂. Further, spark retard remains at S₀. Thus,between t₃ and t₄, although the fuel injection is on, it may remain atF₀, and instead of adjusting the fuel injection amount and intake airflow to compensate for the decrease in desired engine torque, thealternator torque may be increased. By increasing the alternator torquebetween t₃ and t₄, the delivered engine torque may be reduced so thatthe delivered engine torque is approximately the same as the desiredengine torque. As such, the torque error remains constant at T₀, betweent₃ and t₄. In this way, the delivered engine torque may be adjusted tomatch the desired engine torque without adjusting the fuel injection andintake air flow amount in much the same manner as between t₁ and t₂.Said another way, adjustments to the delivered engine torque may be madeby adjusting the alternator torque only, and not adjusting the sparktiming, fuel injection amount, and intake mass air flow between t₃ andt₄.

At t₄, the desired engine torque decreases below D₁. In response to thedesired engine torque decreasing below D₁, fuel injection is turned off,and the amount of fuel injected to the engine is decreased toapproximately zero. In some examples, the amount of fuel injected to theengine is zero. The intake air flow is decreased to I₁ to still allow athreshold amount of air to pass through the engine while fuel is notbeing injected. Additionally at t₄, the alternator torque is decreasedfrom A₂, to A₁. In one example, the alternator torque may be steppeddown from A₂ to A₁. Said another way, the alternator torque may bedecreased from A₂ to A₁, instantaneously, or nearly instantaneously. Insome examples, the alternator torque may be decreased from A₂ to A₁ atthe same time as the fuel injection is turned off. Said another way, thedecrease of the fuel injection, and the decrease in the alternatortorque to A₂ may be simultaneous. However, in other examples, thealternator torque may be decreased from A₂ to A₁ before fuel injectionis turned off. In still further examples, the alternator torque may bedecreased from A₂ to A₁ after fuel injection is turned off. At t₄, thetorque error may remain approximately constant at T₀, since fuelinjection is turned off, but the alternator torque is decreased.

Said another way, the effect of the decrease in fuel injection at t₄, onthe delivered engine torque may be offset by the decrease in alternatortorque. Although the decrease in fuel injection and intake air flow att₄ may cause a decrease in the delivered torque at t₄, the decrease inalternator torque may cause a corresponding increase in deliveredtorque. Thus, by decreasing the fuel injection, while simultaneouslydecreasing the alternator torque at t₄, the delivered torque may beadjusted to match the desired torque. Said another way, decreasing thefuel injection at t₄, without also decreasing the alternator torque mayresult in a delivered torque that would be greater than the desiredengine torque. As a result, the torque error may be less than T₀, if thealternator torque is not decreased at t₄. So, at t₄, the deliveredengine torque is approximately the same as the desired engine torque,and therefore the torque error may remain at T₀. Further, spark retardremains at S₀.

Between t₄ and t₅, the desired engine torque decreases from D₁ to D₀. Inresponse to the decrease in desired engine torque between t₄ and t₅, thealternator torque is monotonically increased from the, lower first levelA₁ to the upper second level A₂. Thus, the alternator torque may beadjusted in inverse proportion to the change in desired engine torque ina similar manner as described above between t₃ and t₄. Fuel injectionremains off at between t₄ and t₅, and the intake air flow remains at thelower first level I₁. Thus, adjustments to the delivered engine torquebetween t₄ and t₅ may be made by adjusting the alternator torque only,and not adjusting the spark timing, fuel injection amount, and intakemass air flow. Further, spark retard remains at S₀.

At t₅, the desired engine torque decreases below D₀. In response to thedesired engine torque decreasing below D₀, the alternator torque may beincreased and maintained at A₂. The torque error remains relativelyconstant at level T₀. Fuel injection remains off at t₅, and the intakeair flow remains at the lower first level I₁. Further, spark retardremains at S₀.

After t₅, the desired engine torque remains relatively constant belowD₀. In response to the desired engine torque remaining approximatelyconstant below D₀, the alternator torque is maintained approximatelyconstant at A₂. The torque error remains relatively constant at levelT₀. Fuel injection remains off at t₅, and the intake air flow remains atthe lower first level I₁. Further, spark retard remains at S₀.

It is important to note that graph 400 shows only an example timeinterval during an engine use. Thus, graph 400 may only show engineoperating conditions during a portion of a single engine use. As such,graph 400 may repeat. Said another way, in some examples graph 400 mayreturn to t₀ after t₅. Further, the desired engine torque may fluctuateback and forth between below D₀ and above D₂ multiple times duringengine use.

Thus, as shown in the FIG. 4, the delivered engine torque may beadjusted by adjusting one or more of the alternator torque, fuelinjection and intake air flow. When the desired engine torque is below alower first level (e.g., D₀) and an intermediate second level (e.g.,D₁), fuel injection may be turned off, and the intake air flow may bereduced to a lower first level (e.g., I₁). As such, when the desiredengine torque is between the lower first level and the intermediatesecond level, changes in the desired engine torque may be met byadjusting only the alternator torque. Specifically, in response to thedesired engine torque increasing between the first and second levels,the alternator torque may be monotonically decreased from an uppersecond level (e.g., A₂) to a lower first level (e.g., A₁). Conversely,the alternator torque may be monotonically increased from the lowerfirst level to the upper second level in response to the desired enginetorque decreasing between the second and first levels.

When the desired engine torque reaches the intermediate second level,the alternator torque may be stepped between the lower first level andsecond level depending on whether the desired engine torque isincreasing or decreasing. If the desired engine torque is decrease atthe intermediate second level, then the alternator torque isinstantaneously or nearly instantaneously stepped down from the uppersecond level to the lower first level. On the other hand, if the desiredengine torque is increasing at the intermediate second level, then thealternator torque is instantaneously or nearly instantaneously steppedup from the lower first level to the upper second level. Further, if theengine torque is increasing at the intermediate second level, then fuelinjection is turned on and adjusted to a threshold amount (e.g., F₀),and the intake air flow is increased to a threshold level (e.g., I₂).However, if the engine torque is decreasing when the engine torquereaches the intermediate second level, fuel injection is turned off, andthe intake air flow is adjusted to the lower first level.

When the desired engine torque is between the intermediate second leveland a higher third level (e.g., D₂), the fuel injection amount andintake air flow are held constant at their respective threshold levels,and only the alternator torque is adjusted to compensate for changes inthe desired engine torque. Specifically, in response to the desiredengine torque increasing between the second and third levels, thealternator torque may be monotonically decreased from the upper secondlevel to the lower first level. Conversely, the alternator torque may bemonotonically increased from the lower first level to the upper secondlevel in response to the desired engine torque decreasing between thethird and second levels.

If the desired engine torque increases above the third level, thealternator torque may remain at the lower first level, while adjustingto the engine torque may be made by adjusting the fuel injection amountand intake air flow. Thus, while fuel injection is off, alternatortorque may be monotonically reduced with increasing desired enginetorque. The alternator torque may then be stepped down to the lowerfirst level to coincide with fuel injection being turned on. Once fuelinjection is turned on, the alternator torque may then be monotonicallyreduced with increasing desired engine torque while the fuel injectionamount and intake air flow may be held constant. When the alternatortorque is reduced to the lower first level, the fuel injection amountand intake air flow may be increased in response to increases in thedesired engine torque. However, in some engine operating conditions,when the fuel injection is turned on and the alternator torque isincreased to the upper second level, the delivered engine torque mayincrease by a greater amount that the desired increase in engine torque.In such situations, as is shown below with reference to FIG. 5, wherethe fuel injection is on, the alternator torque is at the upper secondlevel, and the desired engine torque is less than the delivered enginetorque, spark retard may be employed to reduce the delivered enginetorque, and therefore match the delivered engine torque to the desiredengine torque.

Turning now to FIG. 5, a graph 500 is shown, depicting adjustments to analternator torque based on engine operating conditions. Graph 500 showschanges in the desired engine torque at plot 502, fuel injection at plot504, intake air flow at plot 506, torque error at plot 508, alternatortorque at plot 510, and spark retard at plot 512. Thus, the plots ingraph 500 show the same engine operating conditions as in graph 400shown above in FIG. 4. As such, the desired engine torque at plot 502may be determined and/or estimated in the same manner as described aboveat plot 402 in FIG. 4. Fuel injection at plot 504 may be determinedand/or estimated in the same manner as described above at plot 404 inFIG. 4. Intake air flow at plot 506 may be determined and/or estimatedin the same manner described above at plot 406 in FIG. 4. Torque errormay be determined and/or estimated in the same manner as described aboveat plot 408 in FIG. 4. The alternator torque may be estimated and/oradjusted in the same manner as described above at plot 410 of FIG. 4.Spark retard may be estimated and/or adjusted in the same manner asdescribed above at plot 412 of FIG. 4. Further, all of the levels forthe fuel injection, intake mass air flow, desired engine torque, torqueerror, alternator torque, and spark timing (e.g., A₁, A₂, D₀, D₁, D₂,etc.) are the same as those previously described in FIG. 4

Thus, FIG. 5, may be the same as FIG. 4, except, that in FIG. 5 sparkretard may be employed in certain engine operating conditions, whereasin FIG. 4, spark retard is not used. Specifically, the spark timing asshown in FIG. 5, may be retarded when the fuel injection is on, thealternator torque is at the upper second level, A₂, and the desiredengine torque is less than the delivered engine torque.

Turning now to graph 400 before t₀, the desired engine torque (shown atplot 502) remains below a lower first level D₀. However, the desiredengine torque may increase up to the first level D₀ at t₀. Thus, thedesired engine torque may be increasing before t₀. The lower first levelD₀, may be a threshold level, above which fuel may be injected to theengine to meet the desired torque. As such, fuel injection may remainoff before t₀, as shown at plot 504. Thus, the engine may be in a DFSOcondition before t₀. The intake air flow rate as shown at plot 506, mayremain at approximately a lower first level I₁ before t₀. I₁, may be anair flow rate stored in the memory of the controller to be maintainedwhen fuel injection is off. The alternator torque may be at an uppersecond level A₂, before t₀. The torque error may decrease from an uppersecond level T₂, before t₀, as the desired engine torque increase beforet₀. Despite the fuel injection being off before t₀, and the alternatortorque remaining at the upper second level A₂, the delivered enginetorque may still exceed the desired engine torque before t₀. However, asthe desired engine torque increases before t₀, the torque error maydecrease from T₂, before t₀. Thus, in response to the torque error beinggreater than T₀ before t₀, the alternator torque may be maintained atthe upper second level, A₂. Spark retard remains at a lower first levelS₀, before t₀. The lower first level S₀, may be a level where the sparktiming is not retarded at all. Thus, the spark timing may not beretarded from the set point before t₀.

At t₀, the desired engine torque increases above D₀, and the torqueerror decreases to approximately T₀. In response to the increase indesired engine torque, and the torque error decreasing to approximatelyT₀, the alternator torque may begin to be reduced from the upper secondlevel A₂, at t₀. Fuel injection remains off at t₀, and the intake airflow remains at the lower first level I₁. Further, spark retard remainsat S₀.

Between t₀ and t₁, the desired engine torque increases from D₀, to anintermediate second level D₁. In response to the increase in desiredengine torque between t₀ and t₁, the alternator torque is monotonicallydecreased from the upper second level A₂, to a lower first level A₁. Thelower first level A₁, may be an alternator torque level, below whichwould be insufficient to provide electrical power to various electricaldevices (e.g., electrical loads 48 shown in FIGS. 1-2). However in otherexamples, the lower first level A₁, may be approximately zero, and thepower to support the electrical devices may come from one or morebatteries (e.g., first battery 51 and second battery 46 shown in FIGS.1-2). In still further examples, A₁ may be a non-zero alternator torquelevel that may represent a power output by the alternator that maygreater than zero, but may be insufficient to power the electricaldevices. As such, a portion of the power to the electrical devices maybe provided by one or more of the batteries. Thus, the alternator torquemay be adjusted in inverse proportion to the change in desired enginetorque. Fuel injection remains off at between t₀ and t₁, and the intakeair flow remains at the lower first level I₁. Further, spark retardremains at S₀.

At t₁, the desired engine torque increases above D₁. In response to thedesired engine torque increasing above D₁, fuel injection is turned on,and the amount of fuel injected to the engine is increased to a lowerlevel F₀. The intake air flow is increased according to the increase infuel injection to maintain a desired air/fuel ratio. Thus, the intakeair flow is increased from I₁, to a second level I₂. Said another way,in response to the desired engine torque increasing above D₁, enginecombustion is initiated. Additionally at t₁, the alternator torque maybe increased from A₁, to A₂. In one example, the alternator torque maybe stepped up from A₁ to A₂. Said another way, the alternator torque maybe increased from A₁ to A₂, instantaneously, or nearly instantaneously.In some examples, the alternator torque may be increased from A₁ to A₂at the same time as the fuel injection is turned on. Said another way,the increase of the fuel injection to F₀, and the increase in thealternator torque to A₂ may be simultaneous. However, in other examples,the alternator torque may be increased from A₁ to A₂ before fuelinjection is turned on. At t₁, the torque error may remain approximatelyconstant at T₀, since fuel injection is turned on, but the alternatortorque is increased.

Said another way, the effect of the increase in fuel injection at t₁ onthe delivered engine torque, may be offset by the increase in alternatortorque. Although the increase in fuel injection and intake air flow att₁ may cause an increase in the delivered torque at t₁, the increase inalternator torque may cause a decrease in delivered torque. Thus, byincreasing the fuel injection, while simultaneously increasing thealternator torque at t₁, the delivered torque may be adjusted to matchthe desired torque. Said another way, increasing the fuel injection att₁, without increasing the alternator torque may result in an increasein delivered torque that would be greater than the increase in thedesired engine torque. As a result, the torque error may be greater thanT₀, if the alternator torque is not increased at t₁. However, at t₁, theincrease in alternator torque is not sufficient to offset the increasein engine torque resulting from the fuel injection increasing to F₀.Said another way, increasing the fuel injection while simultaneouslyincreasing alternator torque to A₂ may still result in the deliveredengine torque being greater than the desired engine torque. Thus, at t₁,the torque error increases above T₀. In response to the increase intorque error, spark retard is increased above S₀ at t₁. It is importantto note, that the increase in torque error at t₁ is merely an examplesituation in which the torque error may be greater than T₀. As such, insome examples, not shown in FIG. 5, the torque error may not increaseabove T₀, in response to the initiation of cylinder combustion andincrease in alternator torque at t₁. The example torque error increaseshown at t₁, is used to show an example in which the torque error mayincrease above T₀. However, spark retard may be increased under anyengine operating conditions so long as the alternator torque is at A₂,engine combustion is initiated, and the desired engine torque is lessthan the estimated delivered engine torque.

Between t₁ and t₂, the fuel injection remains at F₀, and accordingly theintake air flow remains at I₂. Additionally, the alternator torqueremains constant at the upper second level A₂ to provide a braking forceon the engine. The desired engine torque continues to increase betweent₁ and t₂. As a result, the torque error may decrease back to T₀ betweent₁ and t₂. The torque error may decrease due to one or more the desiredengine torque increasing, and the increase in spark retard at t₁. Thespark retard may be adjusted between t₁ and t₂, in proportion to theamount of the change in torque error. Thus, as the desired engine torqueincreases, and thereby the amount of torque error decreases, the amountof spark retard may be decreased. As the spark retard results in acorresponding decrease in the engine torque, thereby reducing the torqueerror, the amount of spark retard may be reduced. Thus, the amount ofspark retard may be proportionate to the torque error. Said another way,spark retard may be increased, until the torque error begins todecrease. Once the torque error begins to decrease, the spark retard maybe decreased. Thus, by t₂, the torque error may be reduced toapproximately T₀, and the spark retard may return to S₀.

Between t₂ and t₃, the desired engine torque increases to higher thirdlevel D₂. In response to the increase in desired engine torque betweent₂ and t₃, the alternator torque is monotonically decreased from theupper second level A₂, to a lower first level A₁ in the manner similarto between time t₀ and t₁. Thus, the alternator torque may be adjustedin inverse proportion to the change in desired engine torque. Fuelinjection remains approximately constant at F₀, and the intake air flowremains approximately constant at I₂. Further, spark retard remains atS₀. Thus, between t₂ and t₃, although the fuel injection is on, it mayremain at F₀, and instead of increasing the fuel injection amount andintake air flow to compensate for the increase in desired engine torque,the alternator torque may be reduced. By reducing the alternator torquebetween t₂ and t₃, the delivered engine torque may be increased so thatthe delivered engine torque is approximately the same as the desiredengine torque. As such, the torque error remains constant at T₀, betweent₁ and t₂. In this way, the delivered engine torque may be adjusted tomatch the desired engine torque without adjusting the fuel injection andintake air flow amount. Said another way, adjustments to the deliveredengine torque may be made by adjusting the alternator torque only, andnot adjusting the fuel injection amount, and intake mass air flow.

At t₃, the desired engine torque increases above D₂. In response to thedesired engine torque increasing above D₂, fuel injection is increasedfrom F₀, to levels above F₀ based on an amount of increase in thedesired engine torque. Accordingly, the intake air flow is increasedfrom I₂ to maintain a desired air/fuel ratio. Additionally at t₃, thealternator torque may be remain at the lower first level A₁. Thus, thealternator torque may remain at a level that generates a current and/orvoltage by the alternator sufficient to power one or more of theelectrical devices and/or charge the one or more batteries. As describedabove, since the throttle valve may be located a distance from theengine cylinders, the increase in delivered engine torque due to theincrease in fuel injection and intake air flow at t₃ may not beimmediate. Thus, as shown in the example of FIG. 5 at plot 508, thetorque error may decrease below T₀ to T₁ at t₃. Specifically, thedelivered engine torque may be less than the desired engine torque.However, in other examples, the torque error may remain constant at T₀.Thus, depending on the speed of the intake air flow, and the distancefrom the throttle to the engine cylinders, the delay in the response ofthe delivered engine torque to the increase in fuel injection at t₃ maybe zero, and the increase in fuel injection may provide a nearlyinstantaneous increase in the delivered engine torque. Further, sparkretard remains at S₀.

Between t₃ and t₄, the desired engine torque fluctuates above the higherthird level D₂. In response to changes in the desired engine torquebetween t₃ and t₄, the fuel injection amount and intake air flow areadjusted to match the delivered engine torque to the desired enginetorque. Thus, for increases in the desired engine torque, the fuelinjection amount and intake air flow may be monotonically increased.Further, the fuel injection amount and intake air flow may be adjustedto maintain the desired air/fuel ratio. For decreases in the desiredengine torque the fuel injection amount and intake air flow may bemonotonically decreased. Therefore, the fuel injection amount and intakeair flow may be adjusted in proportion to the amount of increase and/ordecrease in the desired engine torque. Further, if at any time betweent₃ and t₄ the desired engine torque diverges from the delivered enginetorque resulting in a torque error greater or less than T₀, the fuelinjection amount and intake air flow may further be adjusted to matchthe delivered engine torque to the desired engine torque. In this way,the fuel injection amount and intake air flow, may constantly beadjusted based on changes in the desired engine torque so that thedelivered engine torque matches the desired engine torque. As anexample, immediately after t₃, the fuel injection amount and intake airflow may be increased until the torque error returns to approximatelyT₀. Thus, immediately after t₂, the torque error may return toapproximately T₀, and may remain relatively the same at T₀, up to t₄.Additionally between t₃ and t₄, the alternator torque may be remain atthe lower first level A₁. Thus, the alternator torque may remain at alevel sufficient to power one or more of the electrical devices and/orcharge the one or more batteries. Further, spark retard remains at S₀.

At t₄, the desired engine torque decreases below D₂. In response to thedesired engine torque decreasing below D₂, fuel injection is reduced toF₀. Accordingly, the intake air flow is reduced to I₂ to maintain adesired air/fuel ratio. Additionally at t₄, the alternator torque maybegin to be increased from the lower first level A₁. Torque error mayremain relatively the same at T₀. Further, spark retard remains at S₀.

Between t₄ and t₅, the desired engine torque decreases continues todecrease below D₂. In response to the decrease in desired engine torquebetween t₄ and t₅, the alternator torque is monotonically increased fromthe lower first level A₁ to the upper second level A₂. Thus, thealternator torque may be adjusted in inverse proportion to the change indesired engine torque in much the same way as between t₂ and t₃.However, instead of the desired torque increasing and the resultingalternator torque decreasing as between t₂ and t₃, the desired torque isdecreasing and the resulting alternator torque is increasing between t₄and t₅. Fuel injection remains approximately constant at F₀, and theintake air flow remains approximately constant at I₂. Further, sparkretard remains at S₀. Thus, between t₄ and t₅, although the fuelinjection is on, it may remain at F₀, and instead of adjusting the fuelinjection amount and intake air flow to compensate for decreases in thedesired engine torque, the alternator torque may be increased. Byincreasing the alternator torque between t₄ and t₅, the delivered enginetorque may be reduced so that the delivered engine torque isapproximately the same as the desired engine torque. As such, the torqueerror remains constant at T₀, between t₄ and t₅. In this way, thedelivered engine torque may be adjusted to match the desired enginetorque without adjusting the fuel injection and intake air flow amountin much the same manner as between t₂ and t₃. Said another way,adjustments to the delivered engine torque may be made by adjusting thealternator torque only, and not adjusting the spark timing, fuelinjection amount, and intake mass air flow between t₄ and t₅.

At t₅, the fuel injection remains at F₀, and accordingly the intake airflow remains at I₂. Additionally at t₅, the alternator torque isincreased to the upper second level A₂. However, at t₅, the desiredengine torque continues to decrease, and as a result the torque errormay begin to increase above T₀. Since the alternator torque may not beadjusted above A₂, the spark timing is retarded at t₅ in response to thedesired engine torque decreasing at t₅. Thus, at t₅, spark retard isincreased from S₀, to S₁, in the manner described above at t₁.

Between t₅ and t₆, the fuel injection remains at F₀, and accordingly theintake air flow remains at I₂. Additionally, the alternator torqueremains constant at the upper second level A₂ to provide a braking forceon the engine. However, the desired engine torque continues to decreasebetween t₅ and t₆ until it reaches D₁ at t₆. As a result, the torqueerror may continue to increase from the level at t₅. The spark retardmay be adjusted between t₅ and t₆, in proportion to the amount ofdecrease in the desired engine torque, and/or the amount of increase intorque error as described earlier between t₁ and t₂. Thus, as thedesired engine torque decreases, and thereby the amount of torque errorincreases, the amount of spark retard may be increased. As the sparkretard results in a corresponding decrease in the engine torque, therebyreducing the torque error, the amount of spark retard may be reduced asthe torque error is reduced. Thus, the amount of spark retard may beproportionate to the torque error. Said another way, spark retard may beincreased, until the torque error begins to decrease. Once the torqueerror begins to decrease, the spark retard may be decreased. Thus, byt₆, the torque error may be reduced to approximately T₀, and the sparkretard may return to S₀.

At t₆, the desired engine torque decreases below D₁. In response to thedesired engine torque decreasing below D₁, fuel injection is turned off,and the amount of fuel injected to the engine is decreased toapproximately zero. In some examples, the amount of fuel injected to theengine is zero. The intake air flow is decreased to I₁ to still allow athreshold amount of air to pass through the engine while fuel is notbeing injected. Additionally at t₆, the alternator torque is decreasedfrom A₂, to A₁. In one example, the alternator torque may be steppeddown from A₂ to A₁. Said another way, the alternator torque may bedecreased from A₂ to A₁, instantaneously, or nearly instantaneously. Insome examples, the alternator torque may be decreased from A₂ to A₁ atthe same time as the fuel injection is turned off. Said another way, thedecrease of the fuel injection, and the decrease in the alternatortorque to A₂ may be simultaneous. However, in other examples, thealternator torque may be decreased from A₂ to A₁ before fuel injectionis turned off. In still further examples, the alternator torque may bedecreased from A₂ to A₁ after fuel injection is turned off. At t₆, thetorque error may remain approximately constant at T₀, since fuelinjection is turned off, but the alternator torque is decreased.

Said another way, the effect of the decrease in fuel injection at t₆, onthe delivered engine torque may be offset by the decrease in alternatortorque. Although the decrease in fuel injection and intake air flow att₆ may cause a decrease in the delivered torque at t₆, the decrease inalternator torque may cause a corresponding increase in deliveredtorque. Thus, by decreasing the fuel injection, while simultaneouslydecreasing the alternator torque at t₆, the delivered torque may beadjusted to match the desired torque. Said another way, decreasing thefuel injection at t₆, without also decreasing the alternator torque mayresult in a delivered torque that would be greater than the desiredengine torque. As a result, the torque error may be less than T₀, if thealternator torque is not decreased at t₆. So, at t₆, the deliveredengine torque is approximately the same as the desired engine torque,and therefore the torque error may remain at T₀. Further, spark retardremains at S₀.

Between t₆ and t₇, the desired engine torque decreases from D₁to D₀. Inresponse to the decrease in desired engine torque between t₆ and t₇, thealternator torque is monotonically increased from the, lower first levelA₁ to the upper second level A₂. Thus, the alternator torque may beadjusted in inverse proportion to the change in desired engine torque ina similar manner as described above between t₄ and t₅. Fuel injectionremains off between t₆ and t₇, and the intake air flow remains at thelower first level I₁. Further, spark retard remains at S₀. Thus,adjustments to the delivered engine torque between t₆ and t₇ may be madeby adjusting the alternator torque only, and not adjusting the sparktiming, fuel injection amount, and intake mass air flow.

At t₇, the desired engine torque decreases below D₀. In response to thedesired engine torque decreasing below D₀, the alternator torque may beincreased and/or maintained at A₂. The torque error remains relativelyconstant at level T₀. Fuel injection remains off at t₇, and the intakeair flow remains at the lower first level I₁. Further, spark retardremains at S₀.

After t₇, the desired engine torque remains relatively constant belowD₀. In response to the desired engine torque remaining approximatelyconstant below D₀, the alternator torque is maintained approximatelyconstant at A₂. The torque error remains relatively constant at levelT₀. Fuel injection remains off at t₇, and the intake air flow remains atthe lower first level I₁. Further, spark retard remains at S₀.

It is important to note that graph 500 shows only an example timeinterval during an engine use. Thus, graph 500 may only show engineoperating conditions during a portion of a single engine use. As such,graph 500 may repeat. Said another way, in some examples graph 500 mayreturn to t₀ after t₇. Further, the desired engine torque may fluctuateback and forth between below D₀ and above D₂ multiple times duringengine use.

Thus, as shown in the FIG. 5, the delivered engine torque may beadjusted by adjusting one or more of the alternator torque, fuelinjection, intake air flow and spark timing. Spark timing may only beretarded when the fuel injection is on, the alternator torque is at theupper second level, A₂, and the desired engine torque is less than thedelivered engine torque.

In this way, a vehicle system may comprise: an engine with one or morecylinders, an alternator mechanically coupled to the engine, a firstbattery electrically coupled to a starting system for starting thevehicle system and turning on the engine, and selectively electricallycoupled to one or more of the alternator and various electrical loads, asecond battery electrically coupled to the alternator and the electricalloads, a voltage regulator configured to maintain a voltage and/orcurrent supplied to a field coil of the alternator to a set point, and acontroller. The controller may comprise computer readable instructionsfor adjusting the voltage and/or current supplied the field coil betweena first level and a second level based on engine operating conditions.Further, the computer readable instructions may comprise: when notinjecting fuel to the one or more engine cylinders, monotonicallydecreasing the voltage and or current supplied to the field coil withincreasing engine torque demand, and in response to the a desired enginetorque reaching a first threshold, stepping up the current and/orvoltage supplied to the field coil from the first level to the secondlevel. Additionally or alternatively, the computer readable instructionsmay comprise when injecting fuel to the one or more engine cylinders,monotonically decreasing the alternator torque with increasing enginetorque demand from the first threshold to a second threshold, andmaintaining the current and/or voltage supplied to the field coil at thefirst level in response to the engine torque demand increasing above thesecond threshold. In some examples, a load exerted on the engine by thealternator increases with increasing voltage and/or current supplied tothe field coil.

In this way, a technical effect of improving the precision andresponsiveness of engine torque control is achieved, by adjusting thealternator torque during both engine operating conditions where fuelinjection is off (e.g., DFSO conditions) and when fuel is being injectedto one or more engine cylinders. Since adjusting the alternator torqueprovides a more immediate change in engine torque than does adjustingthe intake air flow and/or fuel injection amount, the precision andresponsiveness of the engine torque control may be improved.Specifically, the alternator torque may be monotonically decreased froma higher second level to a lower first level in response to a desiredengine torque increasing above a first threshold. Thus, fuel injectionmay remain off while, the alternator torque is decreased to the lowerfirst level. If the alternator torque reaches the lower first level, andthe desired engine torque continues to increase, then fuel injection maybe turned on, and the alternator torque may be stepped up to the uppersecond level. In some examples, the alternator torque and fuel injectionmay be adjusted simultaneously. In other examples, the alternator torquemay be increased before fuel injection is turned on. Additionally, theincrease in alternator torque from the first level to the second levelmay be instantaneous, or nearly instantaneous.

When the fuel injection is turned on, the resulting increase in enginetorque may be greater than the desired increase in engine torque.However, by increasing the alternator torque from the first level to thesecond level when the fuel injection is turned on, a correspondingdecrease in the desired engine torque is achieved, and thereby excessiveengine torques may be reduced when fuel injection is turned back on fromengine operating conditions such as DFSO. Further, by loading thealternator when turning fuel injection back on, such as when exiting aDFSO condition, the alternator may be used to adjust engine torqueinstead of adjusting the fuel injection amount. Thus, when fuelinjection is turned on, and the alternator torque is increased to theupper second level, further increases in the desired engine torque maybe satisfied by monotonically decreasing the alternator torque from theupper second level. Said another way, fuel injection and intake air flowmay be kept at constant respective levels, while only the alternatortorque may be adjusted to compensate for changes in the desired enginetorque. As such, the amount of fuel injected to the engine when exitinga DFSO, or turning on one or more fuel injectors may be decreased. Thus,another technical effect of increasing the fuel efficiency of the engineby adjusting the alternator torque and not the spark timing is achieved.By loading the alternator when fuel injection is turned on, the usage ofspark retard may be reduced. Instead of reducing the efficiency of theengine by using spark retard, fuel usage may be reduced, while adjustingthe engine torque by adjusting the alternator torque.

Further, another technical effect of increasing the allowable currentand/or voltage output by the alternator is achieved by incorporating twobatteries in a vehicle system. Thus, by increasing the electric powerstorage capacity of a vehicle system by including an additional battery,the current and/or voltage output by the alternator may be adjustedbetween a wider range of values. Thus, the current and/or voltageapplied to an alternator field coil may be adjusted between a widerrange of values, resulting in an increase in the amount of torqueexerted on the engine by the alternator. Said another way, the currentand/or voltage supplied to an alternator may be increased, due to theincreased power that may be accepted by the two battery vehicle system.Thus, the two battery system may be able to absorb the increased currentand/or voltage output by the alternator as a result of the increasedalternator torque. Consequently the load the alternator is capable ofexerting on the engine may be increased. Therefore, the braking forceprovided by the alternator may be increased. As a result, the usage ofspark retard may be reduced, as the effective braking power provided bythe alternator may be increased.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein. Thefollowing claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1-19. (canceled)
 20. A vehicle system comprising: an engine with one ormore cylinders; an alternator mechanically coupled to the engine; afirst battery electrically coupled to a starting system for starting thevehicle system and turning on the engine, and selectively electricallycoupled to one or more of the alternator and various electrical loads; asecond battery electrically coupled to the alternator and the electricalloads; a voltage regulator configured to maintain a voltage and/orcurrent supplied to a field coil of the alternator to a set point; and acontroller with computer readable instructions for adjusting the voltageand/or current supplied to the field coil between a first level and asecond level based on engine operating conditions, where the adjustingcomprises: when not injecting fuel to the one or more engine cylinders,monotonically decreasing the voltage and/or current supplied to thefield coil with increasing engine torque demand, and in response to adesired engine torque reaching a first threshold, stepping up thecurrent and/or voltage supplied to the field coil from the first levelto the second level; when injecting fuel to the one or more enginecylinders, monotonically decreasing an alternator torque with increasingengine torque demand from the first threshold to a second threshold; andmaintaining the current and/or voltage supplied to the field coil at thefirst level in response to the engine torque demand increasing above thesecond threshold.
 21. The system of claim 20, wherein the instructionsfurther include instructions to monotonically decrease alternator torqueto a first torque from a second torque as desired engine torqueincreases, and during cylinder combustion, maintain position of athrottle valve and monotonically decrease alternator torque from thefirst torque to the second torque as desired engine torque increases.22. The system of claim 21, wherein the instruction further includeinstructions to retard spark timing from a desired spark timing duringcylinder combustion, when the alternator torque is at the second level,and engine torque is greater than desired.
 23. A vehicle systemcomprising: an engine with one or more cylinders; an alternatormechanically coupled to the engine; a first battery electrically coupledto a starting system for starting the vehicle system and turning on theengine, and selectively electrically coupled to one or more of thealternator and various electrical loads; a second battery electricallycoupled to the alternator and the electrical loads; a voltage regulatorconfigured to maintain a voltage and/or current supplied to a field coilof the alternator to a set point; and a controller with computerreadable instructions for: during DFSO, when a throttle valve is in afirst position and fuel is not injected to one or more engine cylinders,monotonically decreasing alternator torque to a first torque from asecond torque as desired engine torque increases up to a first level,and during cylinder combustion, maintaining position of the throttlevalve in a second position and monotonically decreasing alternatortorque from the first torque to the second torque as desired enginetorque increases from the first level to a second level.
 24. The systemof claim 23, wherein the instructions further include instructions toadjust the position of the throttle valve between the second positionand a third position as desired engine torque increases above the secondlevel.
 25. The system of claim 23, wherein the instructions furtherinclude instructions to retard spark timing from a desired spark timingduring cylinder combustion, when the alternator torque is at the secondlevel, and engine torque is greater than desired.